Publication Search Results

ID: 157794
Type: article
Authors: Ricci, C.; Kara, E.; Loewenstein, M.; Trakhtenbrot, B.; Arcavi, I.; Remillard, R.; Fabian, A. C.; Gendreau, K. C.; Arzoumanian, Z.; Li, R.; Ho, L. C.; MacLeod, Chelsea L.; Cackett, E.; Altamirano, D.; Gandhi, P.; Kosec, P.; Pasham, D.; Steiner, James; Chan, C. -H
Abstract: We present the drastic transformation of the X-ray properties of the active galactic nucleus (AGN) 1ES 1927+654, following a changing-look event. After the optical/ultraviolet outburst the power-law component, produced in the X-ray corona, disappeared, and the spectrum of 1ES 1927+65 instead became dominated by a blackbody component (kT ∼ 80-120 eV). This implies that the X-ray corona, ubiquitously found in AGNs, was destroyed in the event. Our dense ∼450 days long X-ray monitoring shows that the source is extremely variable in the X-ray band. On long timescales the source varies up to ∼4 dex in ∼100 days, while on short timescales up to ∼2 dex in ∼8 hr. The luminosity of the source is found to first show a strong dip down to $\sim {10}^{40}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$?--> , and then a constant increase in luminosity to levels exceeding the pre-outburst level ≳300 days after the optical event detection, rising up asymptotically to $\sim 2\times {10}^{44}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$?--> . As the X-ray luminosity of the source increases, the X-ray corona is recreated, and a very steep power-law component (Γ ≃ 3) reappears, and dominates the emission for 0.3-2 keV luminosities $\gtrsim {10}^{43.7}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$?--> , ∼300 days after the beginning of the event. We discuss possible origins of this event, and speculate that our observations could be explained by the interaction between the accretion flow and debris from a tidally disrupted star. Our results show that changing-look events can be associated with dramatic and rapid transformations of the innermost regions of accreting supermassive black holes.

ID: 157795
Type: article
Authors: Ahumada, Romina; Allende Prieto, Carlos; Almeida, Andrés; Anders, Friedrich; Anderson, Scott F.; Andrews, Brett H.; Anguiano, Borja; Arcodia, Riccardo; Armengaud, Eric; Aubert, Marie; Avila, Santiago; Avila-Reese, Vladimir; Badenes, Carles; Balland, Christophe; Barger, Kat; Barrera-Ballesteros, Jorge K.; Basu, Sarbani; Bautista, Julian; Beaton, Rachael L.; Beers, Timothy C.; Benavides, B. Izamar T.; Bender, Chad F.; Bernardi, Mariangela; Bershady, Matthew; Beutler, Florian; Bidin, Christian Moni; Bird, Jonathan; Bizyaev, Dmitry; Blanc, Guillermo A.; Blanton, Michael R.; Boquien, Médéric; Borissova, Jura; Bovy, Jo; Brandt, W. N.; Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Bureau, Martin; Burgasser, Adam; Burtin, Etienne; Cano-Díaz, Mariana; Capasso, Raffaella; Cappellari, Michele; Carrera, Ricardo; Chabanier, Solène; Chaplin, William; Chapman, Michael; Cherinka, Brian; Chiappini, Cristina; Doohyun Choi, Peter; Chojnowski, S. Drew; Chung, Haeun; Clerc, Nicolas; Coffey, Damien; Comerford, Julia M.; Comparat, Johan; da Costa, Luiz; Cousinou, Marie-Claude; Covey, Kevin; Crane, Jeffrey D.; Cunha, Katia; da Silva Ilha, Gabriele; Dai, Yu Sophia; Damsted, Sanna B.; Darling, Jeremy; Davidson, James W., Jr.; Davies, Roger; Dawson, Kyle; De, Nikhil; de la Macorra, Axel; De Lee, Nathan; de Andrade Queiroz, Anna Bárbara; Deconto Machado, Alice; de la Torre, Sylvain; Dell'Agli, Flavia; du Mas des Bourboux, Hélion; Diamond-Stanic, Aleksandar M.; Dillon, Sean; Donor, John; Drory, Niv; Duckworth, Chris; Dwelly, Tom; Ebelke, Garrett; Eftekharzadeh, Sarah; Eigenbrot, Arthur Davis; Elsworth, Yvonne P.; Eracleous, Mike; Erfanianfar, Ghazaleh; Escoffier, Stephanie; Fan, Xiaohui; Farr, Emily; Fernández-Trincado, José G.; Feuillet, Diane; Finoguenov, Alexis; Fofie, Patricia; Fraser-McKelvie, Amelia; Frinchaboy, Peter M.; Fromenteau, Sebastien; Fu, Hai; Galbany, Lluís; Garcia, Rafael A.; García-Hernández, D. A.; Garma Oehmichen, Luis Alberto; Ge, Junqiang; Geimba Maia, Marcio Antonio; Geisler, Doug; Gelfand, Joseph; Goddy, Julian; Gonzalez-Perez, Violeta; Grabowski, Kathleen; Green, Paul; Grier, Catherine J.; Guo, Hong; Guy, Julien; Harding, Paul; Hasselquist, Sten; Hawken, Adam James; Hayes, Christian R.; Hearty, Fred; Hekker, S.; Hogg, David W.; Holtzman, Jon A.; Horta, Danny; Hou, Jiamin; Hsieh, Bau-Ching; Huber, Daniel; Hunt, Jason A. S.; Ider Chitham, J.; Imig, Julie; Jaber, Mariana; Jimenez Angel, Camilo Eduardo; Johnson, Jennifer A.; Jones, Amy M.; Jönsson, Henrik; Jullo, Eric; Kim, Yerim; Kinemuchi, Karen; Kirkpatrick, Charles C.,IV; Kite, George W.; Klaene, Mark; Kneib, Jean-Paul; Kollmeier, Juna A.; Kong, Hui; Kounkel, Marina; Krishnarao, Dhanesh; Lacerna, Ivan; Lan, Ting-Wen; Lane, Richard R.; Law, David R.; Le Goff, Jean-Marc; Leung, Henry W.; Lewis, Hannah; Li, Cheng; Lian, Jianhui; Lin, Lihwai; Long, Dan; Longa-Peña, Penélope; Lundgren, Britt; Lyke, Brad W.; Ted Mackereth, J.; MacLeod, Chelsea L.; Majewski, Steven R.; Manchado, Arturo; Maraston, Claudia; Martini, Paul; Masseron, Thomas; Masters, Karen L.; Mathur, Savita; McDermid, Richard M.; Merloni, Andrea; Merrifield, Michael; Mészáros, Szabolcs; Miglio, Andrea; Minniti, Dante; Minsley, Rebecca; Miyaji, Takamitsu; Mohammad, Faizan Gohar; Mosser, Benoit; Mueller, Eva-Maria; Muna, Demitri; Muñoz-Gutiérrez, Andrea; Myers, Adam D.; Nadathur, Seshadri; Nair, Preethi; Nandra, Kirpal; do Nascimento, Janaina Correa; Nevin, Rebecca Jean; Newman, Jeffrey A.; Nidever, David L.; Nitschelm, Christian; Noterdaeme, Pasquier; O'Connell, Julia E.; Olmstead, Matthew D.; Oravetz, Daniel; Oravetz, Audrey; Osorio, Yeisson; Pace, Zachary J.; Padilla, Nelson; Palanque-Delabrouille, Nathalie; Palicio, Pedro A.; Pan, Hsi-An; Pan, Kaike; Parker, James; Paviot, Romain; Peirani, Sebastien; Peña Ramŕez, Karla; Penny, Samantha; Percival, Will J.; Perez-Fournon, Ismael; Pérez-Ràfols, Ignasi; Petitjean, Patrick; Pieri, Matthew M.; Pinsonneault, Marc; Poovelil, Vijith Jacob; Povick, Joshua Tyler; Prakash, Abhishek; Price-Whelan, Adrian M.; Raddick, M. Jordan; Raichoor, Anand; Ray, Amy; Rembold, Sandro Barboza; Rezaie, Mehdi; Riffel, Rogemar A.; Riffel, Rogério; Rix, Hans-Walter; Robin, Annie C.; Roman-Lopes, A.; Román-Zúñiga, Carlos; Rose, Benjamin; Ross, Ashley J.; Rossi, Graziano; Rowlands, Kate; Rubin, Kate H. R.; Salvato, Mara; Sánchez, Ariel G.; Sánchez-Menguiano, Laura; Sánchez-Gallego, José R.; Sayres, Conor; Schaefer, Adam; Schiavon, Ricardo P.; Schimoia, Jaderson S.; Schlafly, Edward; Schlegel, David; Schneider, Donald P.; Schultheis, Mathias; Schwope, Axel; Seo, Hee-Jong; Serenelli, Aldo; Shafieloo, Arman; Shamsi, Shoaib Jamal; Shao, Zhengyi; Shen, Shiyin; Shetrone, Matthew; Shirley, Raphael; Silva Aguirre, Víctor; Simon, Joshua D.; Skrutskie, M. F.; Slosar, Anže; Smethurst, Rebecca; Sobeck, Jennifer; Sodi, Bernardo Cervantes; Souto, Diogo; Stark, David V.; Stassun, Keivan G.; Steinmetz, Matthias; Stello, Dennis; Stermer, Julianna; Storchi-Bergmann, Thaisa; Streblyanska, Alina; Stringfellow, Guy S.; Stutz, Amelia; Suárez, Genaro; Sun, Jing; Taghizadeh-Popp, Manuchehr; Talbot, Michael S.; Tayar, Jamie; Thakar, Aniruddha R.; Theriault, Riley; Thomas, Daniel; Thomas, Zak C.; Tinker, Jeremy; Tojeiro, Rita; Toledo, Hector Hernandez; Tremonti, Christy A.; Troup, Nicholas W.; Tuttle, Sarah; Unda-Sanzana, Eduardo; Valentini, Marica; Vargas-González, Jaime; Vargas-Magaña, Mariana; Vázquez-Mata, Jose Antonio; Vivek, M.; Wake, David; Wang, Yuting; Weaver, Benjamin Alan; Weijmans, Anne-Marie; Wild, Vivienne; Wilson, John C.; Wilson, Robert F.; Wolthuis, Nathan; Wood-Vasey, W. M.; Yan, Renbin; Yang, Meng; Yèche, Christophe; Zamora, Olga; Zarrouk, Pauline; Zasowski, Gail; Zhang, Kai; Zhao, Cheng; Zhao, Gongbo; Zheng, Zheng; Zheng, Zheng; Zhu, Guangtun; Zou, Hu
Abstract: This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).

ID: 157796
Type: article
Authors: Tanner, Angelle; Plavchan, Peter; Bryden, Geoff; Kennedy, Grant; Matrá, Luca; Cronin-Coltsmann, Patrick; Lowrance, Patrick; Henry, Todd; Riaz, Basmah; Gizis, John E.; Riedel, Adric; Choquet, Elodie
Abstract: A set of twenty late-type (K5-M5) stars were observed with the Herschel Space Observatory at 100 and 160 microns with the goal of searching for far-infrared excesses indicative of the presence of circumstellar disks. Out of this sample, four stars (TYC 7443-1102-1, TYC 9340-437-1, GJ 784 and GJ 707) have infrared excesses above their stellar photospheres at either 100 or 160 μm or both. At 100 microns TYC 9340-437-1 is spatially resolved with a shape that suggests it is surrounded by a face-on disk. The 100 μm excess flux associated with GJ 707 is marginal at around 3σ. The excess flux associated with GJ 784 is most likely due to a background galaxy as the dust radius estimated from the spectral energy fit implies that any associated dust disk should have been resolved in the Herschel images but is not. TYC 7443-1102-1 has been observed with ALMA which resolves the emission at its location into two distinct sources making the Herschel excess most likely also due to a background galaxy. It is worth noting that this star is in the 23 Myr old β Pic association. With a disk luminosity on the order of 10^-3 L_*, this system is an ideal follow-up target for high-contrast imaging and ALMA.

ID: 157797
Type: article
Authors: Mirocha, Jordan; Mason, Charlotte; Stark, Daniel P.
Abstract: Connecting the observed rest-ultraviolet (UV) luminosities of high-z galaxies to their intrinsic luminosities (and thus star formation rates, SFRs) requires correcting for the presence of dust. We bypass a common dust-correction approach that uses empirical relationships between infrared (IR) emission and UV colours, and instead augment a semi-empirical model for galaxy formation with a simple - but self-consistent - dust model and use it to jointly fit high-z rest-UV luminosity functions (LFs) and colour-magnitude relations (M_UV-β). In doing so, we find that UV colours evolve with redshift (at fixed UV magnitude), as suggested by observations, even in cases without underlying evolution in dust production, destruction, absorption, or geometry. The observed evolution in our model arises due to the reduction in the mean stellar age and rise in specific SFRs with increasing z. The UV extinction, A_UV, evolves similarly with redshift, though we find a systematically shallower relation between A_UV and M_UV than that predicted by IRX-β relationships derived from z ∼ 3 galaxy samples. Finally, assuming that high $1600\hbox{-}{\mathring{\rm A}}$ transmission (≳0.6) is a reliable Ly α emitter (LAE) indicator, modest scatter in the effective dust surface density of galaxies can explain the evolution both in M_UV-β and LAE fractions. These predictions are readily testable by deep surveys with the James Webb Space Telescope.

ID: 157798
Type: article
Authors: Fuller, S.; Lemaux, B. C.; Bradač, M.; Hoag, A.; Schmidt, K. B.; Huang, K.; Strait, V.; Mason, Charlotte A.; Treu, T.; Pentericci, L.; Trenti, M.; Henry, A.; Malkan, M.
Abstract: We present 36 spectroscopically confirmed intrinsically UV-faint Lyα-emitting galaxies from follow-up observations with Keck/DEep Imaging Multi-Object Spectrograph of gravitationally lensed high-redshift candidates. Candidates were selected to be between 5 ≲ z ≲ 7 from photometric data using Hubble Space Telescope and Spitzer imaging surveys. We performed an integrated photometric redshift probability cut >1% between 5 25 Å at 3σ at the fiducial depth of our survey, and only those galaxies with EW(Lyα) > 25 Å, and only objects with m_AB < 26.8, we found the Lyα emitter (LAE) fraction to be flat or modestly increase from 0.26 ± 0.04 to 0.30 ± 0.04. These values are consistent with a rising LAE fraction with redshift out to z ∼ 6, but at z ∼ 6.5, there is some tension between our results and results from surveys at intrinsically brighter luminosities. We conclude that intrinsically fainter galaxies have Lyα emission, and there is a steep drop in the LAE fraction from our high-redshift sample at z ∼ 6.5 and from similar galaxies at z ∼ 7.5. This likely indicates we are witnessing the tail end of the epoch of reionization, as such a drop is not expected due to changes of intrinsic galaxy properties between these redshifts.

ID: 157799
Type: article
Authors: Venhola, Aku; Peletier, Reynier; Laurikainen, Eija; Salo, Heikki; Iodice, Enrichetta; Mieske, Steffen; Hilker, Michael; Wittmann, Carolin; Lisker, Thorsten; Paolillo, Maurizio; Cantiello, Michele; Janz, Joachim; Spavone, Marilena; D'Abrusco, Raffaele; Ven, Glennvande; Napolitano, Nicola; Kleijn, Gijs Verdoes; Maddox, Natasha; Capaccioli, Massimo; Grado, Aniello; Valentijn, Edwin; Falcón-Barroso, Jesús; Limatola, Luca
Abstract: This article is an erratum for:[https://doi.org/10.1051/0004-6361/201833933]

ID: 157800
Type: article
Authors: Cantiello, Michele; Venhola, Aku; Grado, Aniello; Paolillo, Maurizio; D'Abrusco, Raffaele; Raimondo, Gabriella; Quintini, Massimo; Hilker, Michael; Mieske, Steffen; Tortora, Crescenzo; Spavone, Marilena; Capaccioli, Massimo; Iodice, Enrica; Peletier, Reynier; Barroso, Jesús Falcón; Limatola, Luca; Napolitano, Nicola; Schipani, Pietro; van de Ven, Glenn; Gentile, Fabrizio; Covone, Giovanni
Abstract: Context. A possible pathway for understanding the events and the mechanisms involved in galaxy formation and evolution is an in-depth investigation of the galactic and inter-galactic fossil sub-structures with long dynamical timescales: stars in the field and in stellar clusters.
Aims: This paper continues the Fornax Deep Survey (FDS) series. Following previous studies dedicated to extended Fornax cluster members, we present the catalogs of compact stellar systems in the Fornax cluster, as well as extended background sources and point-like sources.
Methods: We derived ugri photometry of ∼1.7 million sources over the ∼21 square degree area of FDS centered on the bright central galaxy NGC 1399. For a wider area, of ∼27 square degrees extending in the direction of NGC 1316, we provided gri photometry for ∼3.1 million sources. To improve the morphological characterization of sources, we generated multi-band image stacks by coadding the best-seeing gri-band single exposures with a cut at full width at half maximum (FWHM) ≤ 0.″9. We used the multi-band stacks as master detection frames, with a FWHM improved by ∼15% and a FWHM variability from field to field reduced by a factor of ∼2.5 compared to the pass-band with the best FWHM, namely the r-band. The identification of compact sources, in particular, globular clusters (GC), was obtained from a combination of photometric (e.g., colors, magnitudes) and morphometric (e.g., concentration index, elongation, effective radius) selection criteria, also taking as reference the properties of sources with well-defined classifications from spectroscopic or high-resolution imaging data.
Results: Using the FDS catalogs, we present a preliminary analysis of GC distributions in the Fornax area. The study confirms and extends further previous results that were limited to a smaller survey area. We observed the inter-galactic population of GCs, a population of mainly blue GCs centered on NGC 1399, extending over ∼0.9 Mpc, with an ellipticity ∊ ∼ 0.65 and a small tilt in the direction of NGC 1336. Several sub-structures extend over ∼0.5 Mpc along various directions. Two of these structures do not cross any bright galaxy; one of them appears to be connected to NGC 1404, a bright galaxy close to the cluster core and particularly poor in GCs. Using the gri catalogs, we analyze the GC distribution over the extended FDS area and do not find any obvious GC sub-structure bridging the two brightest cluster galaxies, namely, NGC 1316 and NGC 1399. Although NGC 1316 is more than twice as bright of NGC 1399 in optical bands, using gri data, we estimate a GC population that is richer by a factor of ∼3-4 around NGC 1399, as compared to NGC 1316, out to galactocentric distances of ∼40' or ∼230 kpc.
Full Tables 3-6 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/639/A136

ID: 157801
Type: article
Authors: de Menezes, Raniere; D'Abrusco, Raffaele; Massaro, Francesco; Gasparrini, Dario; Nemmen, Rodrigo
Abstract: Associating γ-ray sources to their low-energy counterparts is one of the major challenges of modern γ-ray astronomy. In the context of the Fourth Fermi Large Area Telescope Source Catalog (4FGL), the associations rely mainly on parameters such as apparent magnitude, integrated flux, and angular separation between the γ-ray source and its low-energy candidate counterpart. In this work, we propose a new use of the likelihood ratio (LR) and a complementary supervised learning technique to associate γ-ray blazars in 4FGL, based only on spectral parameters such as the γ-ray photon index, mid-infrared colors, and radio-loudness. In the LR approach, we crossmatch the Wide-field Infrared Survey Explorer Blazar-Like Radio-Loud Sources catalog with 4FGL and compare the resulting candidate counterparts with the sources listed in the γ-ray blazar locus to compute an association probability (AP) for 1138 counterparts. In the supervised learning approach, we train a random forest algorithm with 869 high-confidence blazar associations and 711 fake associations and then compute an AP for 1311 candidate counterparts. A list with all 4FGL blazar candidates of uncertain type associated by our method is provided to guide future optical spectroscopic follow-up observations.

ID: 157802
Type: article
Authors: Olejak, A.; Belczynski, K.; Bulik, T.; Sobolewska, Malgosia
Abstract: Aims: We present an open-access database that includes a synthetic catalog of black holes (BHs) in the Milky Way, divided by the components disk, bulge, and halo. Methods: To calculate the evolution of single and binary stars, we used the updated population synthesis code StarTrack. We applied a new model of the star formation history and chemical evolution of Galactic disk, bulge, and halo that was synthesized from observational and theoretical data. This model can be easily employed for other studies of population evolution. Results: We find that at the current Milky Way (disk+bulge+halo) contains about 1.2 × 10⁸ single BHs with an average mass of about 14 M_☉, and 9.3 × 10⁶ BHs in binary systems with an average mass of 19 M_☉. We present basic statistical properties of the BH population in three Galactic components such as the distributions of BH masses, velocities, or the numbers of BH binary systems in different evolutionary configurations. Conclusions: The metallicity of a stellar population has a significant effect on the final BH mass through the stellar winds. The most massive single BH in our simulation of 113 M_☉ originates from a merger of a BH and a helium star in a low-metallicity stellar environment in the Galactic halo. We constrain that only ∼0.006% of the total Galactic halo mass (including dark matter) can be hidden in the form of stellar origin BHs. These BHs cannot be detected by current observational surveys. We calculated the merger rates for current Galactic double compact objects (DCOs) for two considered common-envelope models: ∼3-81 Myr^-1 for BH-BH, ∼1-9 Myr^-1 for BH-neutron star (NS), and ∼14-59 Myr^-1 for NS-NS systems. We show the evolution of the merger rates of DCOs since the formation of the Milky Way until the current moment with the new star formation model of the Galaxy. Data files are available on our website, http://https://bhc.syntheticuniverse.org/.

ID: 157803
Type: article
Authors: Pokhrel, Riwaj; Gutermuth, Robert A.; Betti, Sarah K.; Offner, Stella S. R.; Myers, Philip C.; Megeath, S. Thomas; Sokol, Alyssa D.; Ali, Babar; Allen, Lori; Allen, Thomas S.; Dunham, Michael M.; Fischer, William J.; Henning, Thomas; Heyer, Mark; Hora, Joseph L.; Pipher, Judith L.; Tobin, John J.; Wolk, Scott J.
Abstract: We explore the relation between the stellar mass surface density and the mass surface density of molecular hydrogen gas in 12 nearby molecular clouds that are located at <1.5 kpc distance. The sample clouds span an order-of-magnitude range in mass, size, and star formation rates. We use thermal dust emission from Herschel maps to probe the gas surface density and the young stellar objects from the most recent Spitzer Extended Solar Neighborhood Archive catalog to probe the stellar surface density. Using a star-sampled nearest neighbor technique to probe the star-gas surface density correlations at the scale of a few parsecs, we find that the stellar mass surface density varies as a power law of the gas mass surface density, with a power-law index of ∼2 in all the clouds. The consistent power-law index implies that star formation efficiency is directly correlated with gas column density, and no gas column density threshold for star formation is observed. We compare the observed correlations with the predictions from an analytical model of thermal fragmentation and with the synthetic observations of a recent hydrodynamic simulation of a turbulent star-forming molecular cloud. We find that the observed correlations are consistent for some clouds with the thermal fragmentation model and can be reproduced using the hydrodynamic simulations.

ID: 157804
Type: article
Authors: Winston, Elaine; Hora, Joseph L.; Tolls, Volker
Abstract: We have conducted a study of star formation in the outer Galaxy from 65°180° in Galactic longitude. Using the DBSCAN method on the combined catalog, we identify 618 clusters or aggregations of YSOs having five or more members. We identify 10,476 class I, 29,604 class II, and 7325 anemic class II/class III YSOs. The ratio of YSOs identified as members of clusters was 25,528/47,338, or 54%. We found that 100 of the clusters identified have previously measured distances in the WISE H II survey. We used these distances in our spectral energy distribution (SED) fitting of the YSOs in these clusters, of which 96 had YSOs with 180° in Galactic longitude. Using the DBSCAN method on the combined catalog, we identify 618 clusters or aggregations of YSOs having five or more members. We identify 10,476 class I, 29,604 class II, and 7325 anemic class II/class III YSOs. The ratio of YSOs identified as members of clusters was 25,528/47,338, or 54%. We found that 100 of the clusters identified have previously measured distances in the WISE H II survey. We used these distances in our spectral energy distribution (SED) fitting of the YSOs in these clusters, of which 96 had YSOs with _☉ for R_{Gal ☉} for R_Gal > 11.5 kpc. The slope of the combined IMF was found to be Γ = 1.92 ± 0.42 above 3 M_☉. These values are consistent with each other within the uncertainties and with literature values in the inner Galaxy high-mass star formation regions. The slopes are likely also consistent with a universal Salpeter IMF.

ID: 157805
Type: article
Authors: Battersby, Cara; Keto, Eric; Walker, Daniel; Barnes, Ashley; Callanan, Daniel; Ginsburg, Adam; Hatchfield, H. Perry; Henshaw, Jonathan; Kauffmann, Jens; Kruijssen, J. M. Diederik; Longmore, Steven N.; Lu, Xing; Mills, Elisabeth A. C.; Pillai, Thushara; Zhang, Qizhou; Bally, John; Butterfield, Natalie; Contreras, Yanett A.; Ho, Luis C.; Ott, Jürgen; Patel, Nimesh; Tolls, Volker
Abstract: We present an overview of the CMZoom survey and its first data release. CMZoom is the first blind, high-resolution survey of the Central Molecular Zone (CMZ; the inner 500 pc of the Milky Way) at wavelengths sensitive to the pre-cursors of high-mass stars. CMZoom is a 550 hr Large Program on the Submillimeter Array that mapped at 1.3 mm all of the gas and dust in the CMZ above a molecular hydrogen column density of 10²³ cm^-2 at a resolution of ∼3″ (0.1 pc). In this paper, we focus on the 1.3 mm dust continuum and its data release, but also describe CMZoom spectral line data which will be released in a forthcoming publication. While CMZoom detected many regions with rich and complex substructure, its key result is an overall deficit in compact substructures on 0.1-2 pc scales (the compact dense gas fraction: CDGF). In comparison with clouds in the Galactic disk, the CDGF in the CMZ is substantially lower, despite having much higher average column densities. CMZ clouds with high CDGFs are well-known sites of active star formation. The inability of most gas in the CMZ to form compact substructures is likely responsible for the dearth of star formation in the CMZ, surprising considering its high density. The factors responsible for the low CDGF are not yet understood but are plausibly due to the extreme environment of the CMZ, having far-reaching ramifications for our understanding of the star formation process across the cosmos.

ID: 157806
Type: article
Authors: Buckley-Geer, E. J.; Lin, H.; Rusu, C. E.; Poh, J.; Palmese, A.; Agnello, A.; Christensen, L.; Frieman, J.; Shajib, A. J.; Treu, T.; Collett, T.; Birrer, S.; Anguita, T.; Fassnacht, C. D.; Meylan, G.; Mukherjee, S.; Wong, K. C.; Aguena, M.; Allam, S.; Avila, S.; Bertin, E.; Bhargava, S.; Brooks, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Costanzi, M.; da Costa, L. N.; De Vicente, J.; Desai, S.; Diehl, H. T.; Doel, P.; Eifler, T. F.; Everett, S.; Flaugher, B.; Fosalba, P.; García-Bellido, J.; Gaztanaga, E.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hinton, S. R.; Honscheid, K.; James, David J.; Kuehn, K.; Kuropatkin, N.; Maia, M. A. G.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Miquel, R.; Ogando, R. L. C.; Paz-Chinchón, F.; Plazas, A. A.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Serrano, S.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Tucker, D. L.; Varga, T. N.; DES Collaboration
Abstract: In time-delay cosmography, three of the key ingredients are (1) determining the velocity dispersion of the lensing galaxy, (2) identifying galaxies and groups along the line of sight with sufficient proximity and mass to be included in the mass model, and (3) estimating the external convergence κ_ext from less massive structures that are not included in the mass model. We present results on all three of these ingredients for two time-delay lensed quad quasar systems, DES J0408-5354 and WGD 2038-4008 . We use the Gemini, Magellan, and VLT telescopes to obtain spectra to both measure the stellar velocity dispersions of the main lensing galaxies and to identify the line-of-sight galaxies in these systems. Next, we identify 10 groups in DES J0408-5354 and two groups in WGD 2038-4008 using a group-finding algorithm. We then identify the most significant galaxy and galaxy-group perturbers using the 'flexion shift' criterion. We determine the probability distribution function of the external convergence κ_ext for both of these systems based on our spectroscopy and on the DES-only multiband wide-field observations. Using weighted galaxy counts, calibrated based on the Millennium Simulation, we find that DES J0408-5354 is located in a significantly underdense environment, leading to a tight (width $\sim 3{{\ \rm per\ cent}}$ ), negative-value κ_ext distribution. On the other hand, WGD 2038-4008 is located in an environment of close to unit density, and its low source redshift results in a much tighter κ_ext of $\sim 1{{\ \rm per\ cent}}$ , as long as no external shear constraints are imposed.

ID: 157807
Type: article
Authors: Fridlund, M.; Livingston, J.; Gandolfi, D.; Persson, C. M.; Lam, K. W. F.; Stassun, K. G.; Hellier, C.; Korth, J.; Hatzes, A. P.; Malavolta, L.; Luque, R.; Redfield, S.; Guenther, E. W.; Albrecht, S.; Barragan, O.; Benatti, S.; Bouma, L.; Cabrera, J.; Cochran, W. D.; Csizmadia, S.; Dai, F.; Deeg, H. J.; Esposito, M.; Georgieva, I.; Grziwa, S.; González Cuesta, L.; Hirano, T.; Jenkins, J. M.; Kabath, P.; Knudstrup, E.; Latham, David W.; Mathur, S.; Mullally, S. E.; Narita, N.; Nowak, G.; Olofsson, A. O. H.; Palle, E.; Pätzold, M.; Pompei, E.; Rauer, H.; Ricker, G.; Rodler, F.; Seager, S.; Serrano, L. M.; Smith, A. M. S.; Spina, L.; Subjak, J.; Tenenbaum, P.; Ting, E. B.; Vanderburg, A.; Vanderspek, R.; Van Eylen, V.; Villanueva, S.; Winn, J. N.
Abstract: We report the discovery of a planetary system orbiting TOI-763(aka CD-39 7945), a V = 10.2, high proper motion G-type dwarf star that was photometrically monitored by the TESS space mission in Sector 10. We obtain and model the stellar spectrum and find an object slightly smaller than the Sun, and somewhat older, but with a similar metallicity. Two planet candidates were found in the light curve to be transiting the star. Combining TESS transit photometry with HARPS high-precision radial velocity (RV) follow-up measurements confirm the planetary nature of these transit signals. We determine masses, radii, and bulk densities of these two planets. A third planet candidate was discovered serendipitously in the RV data. The inner transiting planet, TOI-763 b, has an orbital period of P_b = 5.6 d, a mass of M_b = 9.8 ± 0.8 M_⊕, and a radius of R_b = 2.37 ± 0.10 R_⊕. The second transiting planet, TOI-763 c, has an orbital period of P_c = 12.3 d, a mass of M_c = 9.3 ± 1.0 M_⊕, and a radius of R_c = 2.87 ± 0.11 R_⊕. We find the outermost planet candidate to orbit the star with a period of ∼48 d. If confirmed as a planet, it would have a minimum mass of M_d = 9.5 ± 1.6 M_⊕. We investigated the TESS light curve in order to search for a mono transit by planet d without success. We discuss the importance and implications of this planetary system in terms of the geometrical arrangements of planets orbiting G-type stars.

ID: 157808
Type: article
Authors: Couto, Guilherme S.; Storchi-Bergmann, Thaisa; Siemiginowska, Aneta; Riffel, Rogemar A.; Morganti, Raffaella
Abstract: We investigate the ionized gas excitation and kinematics in the inner $4.3\, \times \, 6.2$ kpc² of the merger radio galaxy 4C+29.30. Using optical integral field spectroscopy with the Gemini North Telescope, we present flux distributions, line-ratio maps, peak velocities and velocity dispersion maps as well as channel maps with a spatial resolution of $\approx\! 955\,$ pc. We observe high blueshifts of up to $\sim\! -650\,$$\rm km\, s^{-1}$ in a region ∼1 arcsec south of the nucleus (the southern knot - SK), which also presents high velocity dispersions ($\sim\! 250\,$$\rm km\, s^{-1}$), which we attribute to an outflow. A possible redshifted counterpart is observed north from the nucleus (the northern knot - NK). We propose that these regions correspond to a bipolar outflow possibly due to the interaction of the radio jet with the ambient gas. We estimate a total ionized gas mass outflow rate of $\dot{M}_{\mathrm{ out}} = 25.4 ^{+11.5 }_{ -7.5}\,$ M_☉ yr^-1with a kinetic power of $\dot{E} = 8.1 ^{+10.7 }_{ -4.0} \times 10^{42}\,$ erg s^-1, which represents $5.8 ^{+7.6 }_{ -2.9} {{\ \rm per\ cent}}$ of the active galactic nucleus (AGN) bolometric luminosity. These values are higher than usually observed in nearby active galaxies with the same bolometric luminosities and could imply a significant impact of the outflows in the evolution of the host galaxy. The excitation is higher in the NK - that correlates with extended X-ray emission, indicating the presence of hotter gas - than in the SK, supporting a scenario in which an obscuring dust lane is blocking part of the AGN radiation to reach the southern region of the galaxy.

ID: 157809
Type: article
Authors: Yan, Zoe Z.; Park, Jee Woo; Ni, Yiqi; Loh, Huanqian; Will, Sebastian; Karman, Tijs; Zwierlein, Martin
Abstract: We demonstrate microwave dressing on ultracold, fermionic ²³Na ⁴⁰K ground-state molecules and observe resonant dipolar collisions with cross sections exceeding 3 times the s -wave unitarity limit. The origin of these interactions is the resonant alignment of the approaching molecules' dipoles along the intermolecular axis, which leads to strong attraction. We explain our observations with a conceptually simple two-state picture based on the Condon approximation. Furthermore, we perform coupled-channel calculations that agree well with the experimentally observed collision rates. The resonant microwave-induced collisions found here enable controlled, strong interactions between molecules, of immediate use for experiments in optical lattices.

ID: 157810
Type: article
Authors: Alderson, L.; Kirk, James; López-Morales, Mercedes; Wheatley, P. J.; Skillen, I.; Henry, G. W.; McGruder, Chima; Brogi, M.; Louden, T.; King, G.
Abstract: We present the optical transmission spectrum of the highly inflated Saturn-mass exoplanet WASP-21b, using three transits obtained with the ACAM instrument on the William Herschel Telescope through the LRG-BEASTS survey (Low Resolution Ground-Based Exoplanet Atmosphere Survey using Transmission Spectroscopy). Our transmission spectrum covers a wavelength range of 4635-9000 Å, achieving an average transit depth precision of 197 ppm compared to one atmospheric scale height at 246 ppm. We detect Na I absorption in a bin width of 30 Å at >4σ confidence, which extends over 100 Å. We see no evidence of absorption from K I. Atmospheric retrieval analysis of the scattering slope indicates it is too steep for Rayleigh scattering from H₂, but is very similar to that of HD 189733b. The features observed in our transmission spectrum cannot be caused by stellar activity alone, with photometric monitoring of WASP-21 showing it to be an inactive star. We therefore conclude that aerosols in the atmosphere of WASP-21b are giving rise to the steep slope that we observe, and that WASP-21b is an excellent target for infrared observations to constrain its atmospheric metallicity.

ID: 157811
Type: article
Authors: Grandis, S.; Klein, M.; Mohr, J. J.; Bocquet, S.; Paulus, M.; Abbott, T. M. C.; Aguena, M.; Allam, S.; Annis, J.; Benson, B. A.; Bertin, E.; Bhargava, S.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Capasso, R.; Costanzi, M.; da Costa, L. N.; De Vicente, J.; Desai, S.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hartley, W. G.; Hinton, S. R.; Hollowood, D. L.; Honscheid, K.; James, David J.; Jeltema, T.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Miquel, R.; Ogando, R. L. C.; Palmese, A.; Paz-Chinchón, F.; Plazas, A. A.; Romer, A. K.; Roodman, A.; Sanchez, E.; Saro, A.; Scarpine, V.; Schubnell, M.; Serrano, S.; Sheldon, E.; Smith, M.; Stark, Antony A.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D. L.; Varga, T. N.; Weller, J.; Wilkinson, R.
Abstract: We construct and validate the selection function of the MARD-Y3 galaxy cluster sample. This sample was selected through optical follow-up of the 2nd ROSAT faint source catalogue with Dark Energy Survey year 3 data. The selection function is modelled by combining an empirically constructed X-ray selection function with an incompleteness model for the optical follow-up. We validate the joint selection function by testing the consistency of the constraints on the X-ray flux-mass and richness-mass scaling relation parameters derived from different sources of mass information: (1) cross-calibration using South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) clusters, (2) calibration using number counts in X-ray, in optical and in both X-ray and optical while marginalizing over cosmological parameters, and (3) other published analyses. We find that the constraints on the scaling relation from the number counts and SPT-SZ cross-calibration agree, indicating that our modelling of the selection function is adequate. Furthermore, we apply a largely cosmology independent method to validate selection functions via the computation of the probability of finding each cluster in the SPT-SZ sample in the MARD-Y3 sample and vice versa. This test reveals no clear evidence for MARD-Y3 contamination, SPT-SZ incompleteness or outlier fraction. Finally, we discuss the prospects of the techniques presented here to limit systematic selection effects in future cluster cosmological studies.

ID: 157812
Type: article
Authors: Wiseman, P.; Pursiainen, M.; Childress, M.; Swann, E.; Smith, M.; Galbany, L.; Lidman, C.; Davis, T. M.; Gutiérrez, C. P.; Möller, A.; Thomas, B. P.; Frohmaier, C.; Foley, R. J.; Hinton, S. R.; Kelsey, L.; Kessler, R.; Lewis, G. F.; Sako, M.; Scolnic, D.; Sullivan, M.; Vincenzi, M.; Abbott, T. M. C.; Aguena, M.; Allam, S.; Annis, J.; Bertin, E.; Bhargava, S.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carollo, D.; Carrasco Kind, M.; Carretero, J.; Costanzi, M.; da Costa, L. N.; Diehl, H. T.; Doel, P.; Everett, S.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Glazebrook, K.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hollowood, D. L.; Honscheid, K.; James, David J.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Menanteau, F.; Miquel, R.; Palmese, A.; Paz-Chinchón, F.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Serrano, S.; Sevilla-Noarbe, I.; Sommer, N. E.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Tucker, B. E.; Tucker, D. L.; Varga, T. N.; Walker, A. R.; DES Collaboration
Abstract: Rapidly evolving transients (RETs), also termed fast blue optical transients, are a recently discovered group of astrophysical events that display rapid luminosity evolution. RETs typically rise to peak in less than 10 d and fade within 30, a time-scale unlikely to be compatible with the decay of Nickel-56 that drives conventional supernovae (SNe). Their peak luminosity spans a range of -15 _g ∼ -9.6), indicating a link to young stellar populations, similar to stripped-envelope SNe. RET hosts appear to show a lack of chemical enrichment, their metallicities akin to long-duration gamma-ray bursts and superluminous SN host galaxies ( ∼ 9.4). There are no clear relationships between mass or SFR of the host galaxies and the peak magnitudes or decline rates of the transients themselves.

ID: 157813
Type: article
Authors: Turbet, Martin; Boulet, Christian; Karman, Tijs
Abstract: Reducing atmospheres have recently emerged as a promising scenario to warm the surface of early Mars enough to drive the formation of valley networks and other ancient aqueous features that have been detected so far on the surface of Mars. Here we present a series of experiments and calculations to better constrain CO₂ + CH₄ and CO₂ + H₂ collision-induced absorptions (CIAs) as well as their effect on the prediction of early Mars surface temperature. First, we carried out a new set of experimental measurements (using the AILES line of the SOLEIL synchrotron) of both CO₂ + CH₄ and CO₂ + H₂ CIAs. These measurements confirm the previous results of Turbet et al. (2019), Icarus vol. 321, while significantly reducing the experimental uncertainties. Secondly, we fitted a semi-empirical model to these CIAs measurements, allowing us to compute the CO₂ + CH₄ and CO₂ + H₂ CIAs across a broad spectral domain (0-1500 cm^-1) and for a wide range of temperatures (100-600 K). Last, we performed 1-D numerical radiative-convective climate calculations (using the LMD Generic Model) to compute the surface temperature expected on the surface of early Mars for several CO₂, CH₄ and H₂ atmospheric contents, taking into account the radiative effect of these revised CIAs. These calculations demonstrate that thick CO₂ + H₂-dominated atmospheres remain a viable solution for warming the surface of Mars above the melting point of water, but not CO₂ + CH₄-dominated atmospheres. Our calculated CO₂ + CH₄ and CO₂ + H₂ CIA spectra and predicted early Mars surface temperatures are provided to the community for future uses.

ID: 157814
Type: article
Authors: Paterson, K.; Fong, W.; Nugent, A.; Escorial, A. Rouco; Leja, Joel; Laskar, T.; Chornock, R.; Miller, A. A.; Scharwächter, J.; Cenko, S. B.; Perley, D.; Tanvir, N. R.; Levan, A.; Cucchiara, A.; Cobb, B. E.; de, K.; Berger, Edo; Terreran, G.; Alexander, K. D.; Nicholl, M.; Blanchard, P. K.; Cornish, D.
Abstract: We present the discovery of the optical afterglow and host galaxy of the Swift short-duration gamma-ray burst (SGRB) GRB 181123B. Observations with Gemini-North starting ≍9.1 hr after the burst reveal a faint optical afterglow with i ≍ 25.1 mag at an angular offset of 0"59 ± 0"16 from its host galaxy. Using grizYJHK observations, we measure a photometric redshift of the host galaxy of $z={1.77}_{-0.17}^{+0.30}$ . From a combination of Gemini and Keck spectroscopy of the host galaxy spanning 4500-18000 Å, we detect a single emission line at 13390 Å, inferred as Hβ at z = 1.754 ± 0.001 and corroborating the photometric redshift. The host galaxy properties of GRB 181123B are typical of those of other SGRB hosts, with an inferred stellar mass of ≍9.1 × 10⁹ M_☉, a mass-weighted age of ≍0.9 Gyr, and an optical luminosity of ≍0.9L*. At z = 1.754, GRB 181123B is the most distant secure SGRB with an optical afterglow detection and one of only three at z > 1.5. Motivated by a growing number of high-z SGRBs, we explore the effects of a missing z > 1.5 SGRB population among the current Swift sample on delay time distribution (DTD) models. We find that lognormal models with mean delay times of ≍4-6 Gyr are consistent with the observed distribution but can be ruled out to 95% confidence, with an additional ≍one to five Swift SGRBs recovered at z > 1.5. In contrast, power-law models with ∝t^-1 are consistent with the redshift distribution and can accommodate up to ≍30 SGRBs at these redshifts. Under this model, we predict that ≍1/3 of the current Swift population of SGRBs is at z > 1. The future discovery or recovery of existing high-z SGRBs will provide significant discriminating power on their DTDs and thus their formation channels.

ID: 157815
Type: article
Authors: Choudhury, Spandan; Pineda, Jaime E.; Caselli, Paola; Ginsburg, Adam; Offner, Stella S. R.; Rosolowsky, Erik; Friesen, Rachel K.; Alves, Felipe O.; Chacón-Tanarro, Ana; Punanova, Anna; Redaelli, Elena; Kirk, Helen; Myers, Philip C.; Martin, Peter G.; Shirley, Yancy; Chun-Yuan Chen, Michael; Goodman, Alyssa A.; di Francesco, James
Abstract: Context. Star formation takes place in cold dense cores in molecular clouds. Earlier observations have found that dense cores exhibit subsonic non-thermal velocity dispersions. In contrast, CO observations show that the ambient large-scale cloud is warmer and has supersonic velocity dispersions. Aims: We aim to study the ammonia (NH₃) molecular line profiles with exquisite sensitivity towards the coherent cores in L1688 in order to study their kinematical properties in unprecedented detail. Methods: We used NH₃ (1,1) and (2,2) data from the first data release (DR1) in the Green Bank Ammonia Survey (GAS). We first smoothed the data to a larger beam of 1' to obtain substantially more extended maps of velocity dispersion and kinetic temperature, compared to the DR1 maps. We then identified the coherent cores in the cloud and analysed the averaged line profiles towards the cores. Results: For the first time, we detected a faint (mean NH₃(1,1) peak brightness (1,1) peak brightness _MB), supersonic component towards all the coherent cores in L1688. We fitted two components, one broad and one narrow, and derived the kinetic temperature and velocity dispersion of each component. The broad components towards all cores have supersonic linewidths (ℳ_S ≥ 1). This component biases the estimate of the narrow dense core component's velocity dispersion by ≈28% and the kinetic temperature by ≈10%, on average, as compared to the results from single-component fits. Conclusions: Neglecting this ubiquitous presence of a broad component towards all coherent cores causes the typical single-component fit to overestimate the temperature and velocity dispersion. This affects the derived detailed physical structure and stability of the cores estimated from NH₃ observations.

ID: 157816
Type: article
Authors: Ramstedt, S.; Vlemmings, W. H. T.; Doan, L.; Danilovich, T.; Lindqvist, M.; Saberi, M.; Olofsson, H.; De Beck, E.; Groenewegen, M. A. T.; Höfner, S.; Kastner, J. H.; Kerschbaum, F.; Khouri, T.; Maercker, M.; Montez, Rodolfo; Quintana-Lacaci, G.; Sahai, R.; Tafoya, D.; Zijlstra, A.
Abstract: Context. This is the first publication from the DEATHSTAR project. The overall goal of the project is to reduce the uncertainties of the observational estimates of mass-loss rates from evolved stars on the Asymptotic Giant Branch (AGB). Aim. The aim in this first publication is to constrain the sizes of the ¹²CO emitting region from the circumstellar envelopes around 42 mostly southern AGB stars, of which 21 are M-type and 21 are C-type, using the Atacama Compact Array (ACA) at the Atacama Large Millimeter/submillimeter Array. The symmetry of the outflows is also investigated. Methods: Line emission from ¹²CO J = 2→1 and 3→2 from all of the sources were mapped using the ACA. In this initial analysis, the emission distribution was fit to a Gaussian distribution in the uv-plane. A detailed radiative transfer analysis will be presented in a future publication. The major and minor axis of the best-fit Gaussian at the line center velocity of the ¹²CO J = 2→1 emission gives a first indication of the size of the emitting region. Furthermore, the fitting results, such as the Gaussian major and minor axis, center position, and the goodness of fit across both lines, constrain the symmetry of the emission distribution. For a subsample of sources, the measured emission distribution is compared to predictions from previous best-fit radiative transfer modeling results. Results: We find that the CO envelope sizes are, in general, larger for C-type than for M-type AGB stars, which is as expected if the CO/H₂ ratio is larger in C-type stars. Furthermore, the measurements show a relation between the measured (Gaussian) ¹²CO J = 2→1 size and circumstellar density that, while in broad agreement with photodissociation calculations, reveals large scatter and some systematic differences between the different stellar types. For lower mass-loss-rate irregular and semi-regular variables of both M- and C-type AGB stars, the ¹²CO J = 2→1 size appears to be independent of the ratio of the mass-loss rate to outflow velocity, which is a measure of circumstellar density. For the higher mass-loss-rate Mira stars, the ¹²CO J = 2→1 size clearly increases with circumstellar density, with larger sizes for the higher CO-abundance C-type stars. The M-type stars appear to be consistently smaller than predicted from photodissociation theory. The majority of the sources have CO envelope sizes that are consistent with a spherically symmetric, smooth outflow, at least on larger scales. For about a third of the sources, indications of strong asymmetries are detected. This is consistent with what was found in previous interferometric investigations of northern sources. Smaller scale asymmetries are found in a larger fraction of sources. Conclusions: These results for CO envelope radii and shapes can be used to constrain detailed radiative transfer modeling of the same stars so as to determine mass-loss rates that are independent of photodissociation models. For a large fraction of the sources, observations at higher spatial resolution will be necessary to deduce the nature and origin of the complex circumstellar dynamics revealed by our ACA observations.The reduced datacubes are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A133

ID: 157817
Type: article
Authors: Mayer, Martin; Becker, Werner; Patnaude, Daniel; Winkler, P. Frank; Kraft, Ralph
Abstract: We present an improved proper-motion measurement of the central compact object RX J0822-4300, located in the supernova remnant Puppis A. By employing a new data set taken in 2019 February by the High Resolution Camera on board the Chandra X-ray Observatory, we approximately double the available temporal baseline for our analysis to slightly more than 19 yr (7000 days). We correct for the astrometric inaccuracy of Chandra using calibrator stars with known optical positions that are detected in all observations. Thereby, we obtain absolute positions of RX J0822-4300 accurate to around $0\buildrel{\prime\prime}\over{.} 1$ and from these a new best estimate for its total proper motion of ${\mu }_{\mathrm{tot}}=(80.4\pm 7.7)\,\mathrm{mas}\,{\mathrm{yr}}^{-1}$. For a remnant distance of 2 kpc, this corresponds to a projected kick velocity of $(763\pm 73)\ \,\mathrm{km}\,{{\rm{s}}}^{-1}$ at a position angle of ${\phi }_{0}={(247.8\pm 4.4)}^{\circ }$. The proper-motion measurement of RX J0822-4300 is used for discussing the kinematic age of Puppis A.

ID: 157818
Type: article
Authors: Jacobson-Galán, Wynn V.; Margutti, Raffaella; Kilpatrick, Charles D.; Hiramatsu, Daichi; Perets, Hagai; Khatami, David; Foley, Ryan J.; Raymond, John; Yoon, Sung-Chul; Bobrick, Alexey; Zenati, Yossef; Galbany, Lluís; Andrews, Jennifer; Brown, Peter J.; Cartier, Régis; Coppejans, Deanne L.; Dimitriadis, Georgios; Dobson, Matthew; Hajela, Aprajita; Howell, D. Andrew; Kuncarayakti, Hanindyo; Milisavljevic, Danny; Rahman, Mohammed; Rojas-Bravo, César; Sand, David J.; Shepherd, Joel; Smartt, Stephen J.; Stacey, Holland; Stroh, Michael; Swift, Jonathan J.; Terreran, Giacomo; Vinko, Jozsef; Wang, Xiaofeng; Anderson, Joseph P.; Baron, Edward A.; Berger, Edo; Blanchard, Peter K.; Burke, Jamison; Coulter, David A.; DeMarchi, Lindsay; Derkacy, James M.; Fremling, Christoffer; Gomez, Sebastian; Gromadzki, Mariusz; Hosseinzadeh, Griffin; Kasen, Daniel; Kriskovics, Levente; McCully, Curtis; Müller-Bravo, Tomás E.; Nicholl, Matt; Ordasi, András; Pellegrino, Craig; Piro, Anthony L.; Pál, András; Ren, Juanjuan; Rest, Armin; Rich, R. Michael; Sai, Hanna; Sárneczky, Krisztián; Shen, Ken J.; Short, Philip; Siebert, Matthew R.; Stauffer, Candice; Szakáts, Róbert; Zhang, Xinhan; Zhang, Jujia; Zhang, Kaicheng
Abstract: We present panchromatic observations and modeling of the Calcium-rich supernova (SN) 2019ehk in the star-forming galaxy M100 (d ≍ 16.2 Mpc) starting 10 hr after explosion and continuing for ∼300 days. SN 2019ehk shows a double-peaked optical light curve peaking at t = 3 and 15 days. The first peak is coincident with luminous, rapidly decaying Swift-XRT-discovered X-ray emission ( ${L}_{{\rm{x}}}\approx {10}^{41}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ at 3 days; L_x ∝ t^-3), and a Shane/Kast spectral detection of narrow Hα and He II emission lines (v ≍ 500 $\mathrm{km}\,{{\rm{s}}}^{-1}$ ) originating from pre-existent circumstellar material (CSM). We attribute this phenomenology to radiation from shock interaction with extended, dense material surrounding the progenitor star at r ), and a Shane/Kast spectral detection of narrow Hα and He II emission lines (v ≍ 500 $\mathrm{km}\,{{\rm{s}}}^{-1}$ ) originating from pre-existent circumstellar material (CSM). We attribute this phenomenology to radiation from shock interaction with extended, dense material surrounding the progenitor star at r ¹⁵ cm and the resulting cooling emission. We calculate a total CSM mass of ∼7 × 10^-3 ${M}_{\odot }$ (M_He/M_H ≍6) with particle density n ≍ 10⁹ cm^-3. Radio observations indicate a significantly lower density n . Radio observations indicate a significantly lower density n ⁴ cm^-3 at larger radii r > (0.1-1) × 10¹⁷ cm. The photometric and spectroscopic properties during the second light-curve peak are consistent with those of Ca-rich transients (rise-time of t_r = 13.4 ± 0.210 days and a peak B-band magnitude of M_B = -15.1 ± 0.200 mag). We find that SN 2019ehk synthesized (3.1 ± 0.11) × 10^-2 ${M}_{\odot }$ of ${}^{56}\mathrm{Ni}$ and ejected M_ej = (0.72 ± 0.040) ${M}_{\odot }$ total with a kinetic energy E_k = (1.8 ± 0.10) × 10⁵⁰ erg. Finally, deep HST pre-explosion imaging at the SN site constrains the parameter space of viable stellar progenitors to massive stars in the lowest mass bin (∼10 ${M}_{\odot }$ ) in binaries that lost most of their He envelope or white dwarfs (WDs). The explosion and environment properties of SN 2019ehk further restrict the potential WD progenitor systems to low-mass hybrid HeCO WD+CO WD binaries.

ID: 157819
Type: article
Authors: Abdalla, H.; Adam, R.; Aharonian, F.; Ait Benkhali, F.; Angüner, E. O.; Arakawa, M.; Arcaro, C.; Armand, C.; Ashkar, H.; Backes, M.; Barbosa Martins, V.; Barnard, M.; Becherini, Y.; Berge, D.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; Bregeon, J.; Breuhaus, M.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Bylund, T.; Caroff, S.; Carosi, A.; Casanova, S.; Cerruti, M.; Chand, T.; Chandra, S.; Chen, A.; Colafrancesco, S.; Curyło, M.; Davids, I. D.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Dmytriiev, A.; Donath, A.; Doroshenko, V.; Dyks, J.; Egberts, K.; Emery, G.; Ernenwein, J. -P; Eschbach, S.; Feijen, K.; Fegan, S.; Fiasson, A.; Fontaine, G.; Funk, S.; Füßling, M.; Gabici, S.; Gallant, Y. A.; Gaté, F.; Giavitto, G.; Giunti, L.; Glawion, D.; Glicenstein, J. F.; Gottschall, D.; Grondin, M. -H; Hahn, J.; Haupt, M.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.; Horns, D.; Huber, D.; Iwasaki, H.; Jamrozy, M.; Jankowsky, D.; Jankowsky, F.; Jardin-Blicq, A.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Khangulyan, D.; Khélifi, B.; King, J.; Klepser, S.; Kluźniak, W.; Komin, Nu; Kosack, K.; Kostunin, D.; Kreter, M.; Lamanna, G.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P; Leser, E.; Levy, C.; Lohse, T.; Lypova, I.; Mackey, J.; Majumdar, J.; Malyshev, D.; Marandon, V.; Marcowith, A.; Mares, A.; Mariaud, C.; Martí-Devesa, G.; Marx, R.; Maurin, G.; Meintjes, P. J.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Moore, C.; Moulin, E.; Muller, J.; Murach, T.; Nakashima, S.; de Naurois, M.; Ndiyavala, H.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; de Ona Wilhelmi, E.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Perennes, C.; Petrucci, P. -O; Peyaud, B.; Piel, Q.; Pita, S.; Poireau, V.; Priyana Noel, A.; Prokhorov, D. A.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Rauth, R.; Reimer, A.; Reimer, O.; Remy, Q.; Renaud, M.; Rieger, F.; Rinchiuso, L.; Romoli, C.; Rowell, G.; Rudak, B.; Ruiz-Velasco, E.; Sahakian, V.; Sailer, S.; Saito, S.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schutte, H. M.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Senniappan, M.; Seyffert, A. S.; Shafi, N.; Shiningayamwe, K.; Simoni, R.; Sinha, A.; Sol, H.; Specovius, A.; Spir-Jacob, M.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steppa, C.; Takahashi, T.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsirou, M.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Vincent, P.; Vink, J.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; White, R.; Wierzcholska, A.; Yang, R.; Yoneda, H.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zorn, J.; Żywucka, N.; Madejski, G. M.; Nalewajko, K.; Madsen, K. K.; Chiang, J.; Baloković, Mislav; Paneque, D.; Furniss, A. K.; Hayashida, M.; Urry, C. M.; Ajello, M.; Harrison, F. A.; Giebels, B.; Stern, D.; Forster, K.; Giommi, P.; Perri, M.; Puccetti, S.; Zoglauer, A.; Tagliaferri, G.
Abstract: Here we report the results of the first ever contemporaneous multi-wavelength observation campaign on the BL Lac object PKS 2155-304 involving Swift, NuSTAR, Fermi-LAT, and H.E.S.S. The use of these instruments allows us to cover a broad energy range, which is important for disentangling the different radiative mechanisms. The source, observed from June 2013 to October 2013, was found in a low flux state with respect to previous observations but exhibited highly significant flux variability in the X-rays. The high-energy end of the synchrotron spectrum can be traced up to 40 keV without significant contamination by high-energy emission. A one-zone synchrotron self-Compton model was used to reproduce the broadband flux of the source for all the observations presented here but failed for previous observations made in April 2013. A lepto-hadronic solution was then explored to explain these earlier observational results.

ID: 157748
Type: article
Authors: Käfer, Florian; Finoguenov, Alexis; Eckert, Dominique; Clerc, Nicolas; Ramos-Ceja, Miriam E.; Sanders, Jeremy S.; Ghirardini, Vittorio
Abstract: Context. One key ingredient in using galaxy clusters as a precision cosmological probe in large X-ray surveys is understanding selection effects. The dependence of the X-ray emission on the square of the gas density leads to a predominant role of cool cores in the detection of galaxy clusters. The contribution of cool cores to the X-ray luminosity does not scale with cluster mass and cosmology and therefore affects the use of X-ray clusters in producing cosmological constraints.
Aims: One of the main science goals of the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) mission is to constrain cosmology with a wide X-ray survey. We propose an eROSITA galaxy cluster detection scheme that avoids the use of X-ray cluster centers in detection. We calculate theoretical expectations and characterize the performance of this scheme by simulations.
Methods: We performed Monte Carlo simulations of the upcoming eROSITA mission, including known foreground and background components. By performing realistic simulations of point sources in survey mode, we searched for spatial scales where the extended signal is not contaminated by the point-source flux. We derive a combination of scales and thresholds, which result in a clean extended source catalog. We designed the output of the cluster detection, which enables calibrating the core-excised luminosity using external mass measurements. We provide a way to incorporate the results of this calibration in producing the final core-excised luminosity.
Results: Similarly to other galaxy cluster detection pipelines, we sample the detection space of the flux - cluster core radius of our method and find many similarities with the pipeline used in the 400d survey. Both detection methods require large statistics on compact clusters in order to reduce the contamination from point sources. The benefit of our pipeline consists of the sensitivity to the outer cluster shapes, which are characterized by large core sizes with little cluster to cluster variation at a fixed total mass of the cluster.
Conclusions: Galaxy cluster detection through cluster outskirts improves the cluster characterization using eROSITA survey data and is expected to yield well-characterized cluster catalogs with simple selection functions.

ID: 157749
Type: article
Authors: Verliat, Antoine; Hennebelle, Patrick; Maury, Anaëlle J.; Gaudel, Mathilde
Abstract: Context. Planet-forming disks are fundamental objects that are thought to be inherited from large scale rotation through the conservation of angular momentum during the collapse of a prestellar dense core.
Aims: We investigate the possibility for a protostellar disk to be formed from a motionless dense core that contains nonaxisymmetric density fluctuations. The rotation is thus generated locally by the asymmetry of the collapse.
Methods: We study the evolution of the angular momentum in a nonaxisymmetric collapse of a dense core from an analytical point of view. To test the theory, we performed three-dimensional simulations of a collapsing prestellar dense core using adaptative mesh refinement. We started from a nonaxisymmetrical situation, considering a dense core with random density perturbations that follow a turbulence spectrum. We analyzed the emerging disk by comparing the angular momentum it contains with the one expected from our analytic development. We studied the velocity gradients at different scales in the simulation as is done with observations.
Results: We show that the angular momentum in the frame of a stellar object, which is not located at the center of mass of the core, is not conserved due to inertial forces. Our simulations of such nonaxisymmetrical collapse quickly produce accretion disks at the small scales in the core. The analysis of the kinematics at different scales in the simulated core reveals projected velocity gradients of amplitudes similar to the ones observed in protostellar cores and for which directions vary, sometimes even reversing when small and large scales are compared. These complex kinematics patterns appear in recent observations and could be a discriminating feature with models where rotation is inherited from large scales. Our results from simulations without initial rotation are more consistent with these recent observations than when solid-body rotation is initially imprinted. Lastly, we show that the disks that formed in this scenario of nonaxisymmetrical gravitational collapse grow to reach sizes larger than those that are observed, and then fragment. We show that including a magnetic field in these simulations reduces the size of the outcoming disks and it prevents them from fragmenting, as is shown by previous studies.
Conclusions: We show that in a nonaxisymmetrical collapse, the formation of a disk can be induced by small perturbations of the initial density field in the core, even in the absence of global large-scale rotation of the core. In this scenario, large disks are generic features that are natural consequences of the hydrodynamical fluid interactions and self-gravity. Since recent observations have shown that most disks are significantly smaller and have a size of a few tens of astronomical units, our study suggests that magnetic braking is the most likely explanation. The kinematics of our model are consistent with typically observed values of velocity gradients and specific angular momentum in protostellar cores. These results open a new avenue in which our understanding of the early phases of disk formation can be explored since they suggest that a fraction of the protostellar disks could be the product of nonaxisymmetrical collapse, rather than directly resulting from the conservation of preexisting large scale angular momentum in rotating cores.

ID: 157750
Type: article
Authors: Belloche, A.; Maury, Anaëlle J.; Maret, S.; Anderl, S.; Bacmann, A.; André, Ph; Bontemps, S.; Cabrit, S.; Codella, C.; Gaudel, M.; Gueth, F.; Lefèvre, C.; Lefloch, B.; Podio, L.; Testi, L.
Abstract: Context. Complex organic molecules (COMs) have been detected in a few Class 0 protostars but their origin is not well understood. While the usual picture of a hot corino explains their presence as resulting from the heating of the inner envelope by the nascent protostar, shocks in the outflow, disk wind, the presence of a flared disk, or the interaction region between envelope and disk at the centrifugal barrier have also been claimed to enhance the abundance of COMs.
Aims: Going beyond studies of individual objects, we want to investigate the origin of COMs in young protostars on a statistical basis.
Methods: We use the CALYPSO survey performed with the Plateau de Bure Interferometer of the Institut de Radioastronomie Millimétrique to search for COMs at high angular resolution in a sample of 26 solar-type protostars, including 22 Class 0 and four Class I objects. We derive the column densities of the detected molecules under the local thermodynamic equilibrium approximation and search for correlations between their abundances and with various source properties.
Results: Methanol is detected in 12 sources and tentatively in one source, which represents half of the sample. Eight sources (30%) have detections of at least three COMs. We find a strong chemical differentiation in multiple systems with five systems having one component with at least three COMs detected but the other component devoid of COM emission. All sources with a luminosity higher than 4 L_☉ have at least one detected COM whereas no COM emission is detected in sources with internal luminosity lower than 2 L_☉, likely because of a lack of sensitivity. Internal luminosity is found to be the source parameter impacting the COM chemical composition of the sources the most, while there is no obvious correlation between the detection of COM emission and that of a disk-like structure. A canonical hot-corino origin may explain the COM emission in four sources, an accretion-shock origin in two or possibly three sources, and an outflow origin in three sources. The CALYPSO sources with COM detections can be classified into three groups on the basis of the abundances of oxygen-bearing molecules, cyanides, and CHO-bearing molecules. These chemical groups correlate neither with the COM origin scenarios, nor with the evolutionary status of the sources if we take the ratio of envelope mass to internal luminosity as an evolutionary tracer. We find strong correlations between molecules that are a priori not related chemically (for instance methanol and methyl cyanide), implying that the existence of a correlation does not imply a chemical link.
Conclusions: The CALYPSO survey has revealed a chemical differentiation in multiple systems that is markedly different from the case of the prototypical binary IRAS 16293-2422. This raises the question of whether all low-mass protostars go through a phase showing COM emission. A larger sample of young protostars and a more accurate determination of their internal luminosity will be necessary to make further progress. Searching for correlations between the COM emission and the jet/outflow properties of the sources may also be promising.
Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).
The CALYPSO calibrated visibility tables and maps are publicly available at http://www.iram-institute.org/EN/content-page-317-7-158-240-317-0.html

ID: 157751
Type: article
Authors: Gaudel, M.; Maury, Anaëlle J.; Belloche, A.; Maret, S.; André, Ph; Hennebelle, P.; Galametz, M.; Testi, L.; Cabrit, S.; Palmeirim, P.; Ladjelate, B.; Codella, C.; Podio, L.
Abstract: Context. Understanding the initial properties of star forming material and how they affect the star formation process is a key question. The infalling gas must redistribute most of its initial angular momentum inherited from prestellar cores before reaching the central stellar embryo. Disk formation has been naturally considered as a possible solution to this "angular momentum problem". However, how the initial angular momentum of protostellar cores is distributed and evolves during the main accretion phase and the beginning of disk formation has largely remained unconstrained up to now.
Aims: In the framework of the IRAM CALYPSO survey, we obtained observations of the dense gas kinematics that we used to quantify the amount and distribution of specific angular momentum at all scales in collapsing-rotating Class 0 protostellar envelopes.
Methods: We used the high dynamic range C¹⁸O (2-1) and N₂H⁺ (1-0) datasets to produce centroid velocity maps and probe the rotational motions in the sample of 12 envelopes from scales ~50 to ~5000 au.
Results: We identify differential rotation motions at scales ≲1600 au in 11 out of the 12 protostellar envelopes of our sample by measuring the velocity gradient along the equatorial axis, which we fit with a power-law model v ∝ r^α. This suggests that coherent motions dominate the kinematics in the inner protostellar envelopes. The radial distributions of specific angular momentum in the CALYPSO sample suggest the following two distinct regimes within protostellar envelopes: the specific angular momentum decreases as j ∝ r^1.6±0.2 down to ~1600 au and then tends to become relatively constant around ~6 × 10^-4 km s^-1 pc down to ~50 au.
Conclusions: The values of specific angular momentum measured in the inner Class 0 envelopes suggest that material directly involved in the star formation process (1600 au, suggesting that these gradients may not be directly related to rotational motions of the envelopes. We conclude that the specific angular momentum observed at these scales could find its origin in other mechanisms, such as core-forming motions (infall, turbulence), or trace an imprint of the initial conditions for the formation of protostellar cores.
The datasets used in this paper are available at http://www.iram.fr/ILPA/LP010/

ID: 157752
Type: article
Authors: Lucas, P. W.; Minniti, D.; Kamble, Atish; Kaplan, D. L.; Cross, N.; Dekany, I.; Ivanov, V. D.; Kurtev, R.; Saito, R. K.; Smith, L. C.; Catelan, M.; Masetti, N.; Toledo, I.; Hempel, M.; Thompson, M. A.; Contreras Peña, C.; Forbrich, J.; Krause, M.; Dale, J.; Borissova, J.; Emerson, J.
Abstract: A search of the first Data Release of the VISTA Variables in the Via Lactea (VVV) Survey discovered the exceptionally red transient VVV-WIT-01 (H - K_s = 5.2). It peaked before March 2010, then faded by ∼9.5 mag over the following 2 yr. The 1.6-22 μm spectral energy distribution in March 2010 was well fit by a highly obscured blackbody with T ∼ 1000 K and A_{K_s} ∼ 6.6 mag. The source is projected against the Infrared Dark Cloud (IRDC) SDC G331.062-0.294. The chance projection probability is small for any single event (p ≈ 0.01-0.02), which suggests a physical association, e.g. a collision between low mass protostars. However, blackbody emission at T ∼ 1000 K is common in classical novae (especially CO novae) at the infrared peak in the light curve due to condensation of dust ∼30-60 d after the explosion. Radio follow-up with the Australia Telescope Compact Array detected a fading continuum source with properties consistent with a classical nova but probably inconsistent with colliding protostars. Considering all VVV transients that could have been projected against a catalogued IRDC raises the probability of a chance association to p = 0.13-0.24. After weighing several options, it appears likely that VVV-WIT-01 was a classical nova event located behind an IRDC.

ID: 157753
Type: article
Authors: Samajdar, Rhine; Ho, Wen Wei; Pichler, Hannes; Lukin, Mikhail D.; Sachdev, Subir
Abstract: We describe the zero-temperature phase diagram of a model of a two-dimensional square-lattice array of neutral atoms, excited into Rydberg states and interacting via strong van der Waals interactions. Using the density-matrix renormalization group algorithm, we map out the phase diagram and obtain a rich variety of phases featuring complex density wave orderings, upon varying lattice spacing and laser detuning. While some of these phases result from the classical optimization of the van der Waals energy, we also find intrinsically quantum-ordered phases stabilized by quantum fluctuations. These phases are surrounded by novel quantum phase transitions, which we analyze by finite-size scaling numerics and Landau theories. Our work highlights Rydberg quantum simulators in higher dimensions as promising platforms to realize exotic many-body phenomena.

ID: 157754
Type: article
Authors: Chattopadhyay, Sambuddha; Pichler, Hannes; Lukin, Mikhail D.; Ho, Wen Wei
Abstract: We study weak ergodicity breaking in a one-dimensional, nonintegrable spin-1 XY model. We construct for it an exact, highly excited eigenstate, which despite its large energy density, can be represented analytically by a finite bond-dimension matrix product state (MPS) with area-law entanglement. Upon a quench to a finite Zeeman field, the state undergoes periodic dynamics with perfect many-body revivals, in stark contrast to other generic initial states which instead rapidly thermalize. This dynamics can be completely understood in terms of the evolution of entangled virtual spin-1/2 degrees of freedom, which in turn underpin the presence of an extensive tower of strong-eigenstate thermalization hypothesis (ETH)-violating many-body eigenstates. The resulting quantum many-body scars are therefore of novel origin. Our results provide important analytical insights into the nature and entanglement structure of quantum many-body scars.

ID: 157755
Type: article
Authors: Zhou, Leo; Wang, Sheng-Tao; Choi, Soonwon; Pichler, Hannes; Lukin, Mikhail D.
Abstract: The quantum approximate optimization algorithm (QAOA) is a hybrid quantum-classical variational algorithm designed to tackle combinatorial optimization problems. Despite its promise for near-term quantum applications, not much is currently understood about the QAOA's performance beyond its lowest-depth variant. An essential but missing ingredient for understanding and deploying the QAOA is a constructive approach to carry out the outer-loop classical optimization. We provide an in-depth study of the performance of the QAOA on MaxCut problems by developing an efficient parameter-optimization procedure and revealing its ability to exploit nonadiabatic operations. Building on observed patterns in optimal parameters, we propose heuristic strategies for initializing optimizations to find quasioptimal p -level QAOA parameters in O [poly (p )] time, whereas the standard strategy of random initialization requires 2^{O (p )} optimization runs to achieve similar performance. We then benchmark the QAOA and compare it with quantum annealing, especially on difficult instances where adiabatic quantum annealing fails due to small spectral gaps. The comparison reveals that the QAOA can learn via optimization to utilize nonadiabatic mechanisms to circumvent the challenges associated with vanishing spectral gaps. Finally, we provide a realistic resource analysis on the experimental implementation of the QAOA. When quantum fluctuations in measurements are accounted for, we illustrate that optimization is important only for problem sizes beyond numerical simulations but accessible on near-term devices. We propose a feasible implementation of large MaxCut problems with a few hundred vertices in a system of 2D neutral atoms, reaching the regime to challenge the best classical algorithms.

ID: 157756
Type: article
Authors: Bekenstein, Rivka; Pikovski, Igor; Pichler, Hannes; Shahmoon, E.; Yelin, S. F.; Lukin, M. D.
Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.

ID: 157757
Type: article
Authors: Borregaard, Johannes; Pichler, Hannes; Schröder, Tim; Lukin, Mikhail D.; Lodahl, Peter; Sørensen, Anders S.
Abstract: We propose a novel one-way quantum repeater architecture based on photonic tree-cluster states. Encoding a qubit in a photonic tree cluster protects the information from transmission loss and enables long-range quantum communication through a chain of repeater stations. As opposed to conventional approaches that are limited by the two-way communication time, the overall transmission rate of the current quantum repeater protocol is determined by the local processing time enabling very high communication rates. We further show that such a repeater can be constructed with as little as two stationary qubits and one quantum emitter per repeater station, which significantly increases the experimental feasibility. We discuss potential implementations with diamond defect centers and semiconductor quantum dots efficiently coupled to photonic nanostructures and outline how such systems may be integrated into repeater stations.

ID: 157758
Type: article
Authors: Bekenstein, Rivka; Pikovski, Igor; Pichler, Hannes; Shahmoon, E.; Yelin, S. F.; Lukin, M. D.
Abstract: Metasurfaces mould the flow of classical light waves by engineering subwavelength patterns from dielectric or metallic thin films. We introduce and analyse a method in which quantum operator-valued reflectivity can be used to control both the spatiotemporal and quantum properties of transmitted and reflected light. Such quantum metasurfaces are realized by entangling the macroscopic response of atomically thin atom arrays to light. We show that such a system allows for parallel quantum operations between atoms and photons as well as for the generation of highly entangled photonic states such as photonic Greenberger-Horne-Zeilinger and three-dimensional cluster states suitable for quantum information processing. We analyse the influence of imperfections as well as specific implementations based on atom arrays excited into Rydberg states.

ID: 157759
Type: article
Authors: Barausse, Enrico; Berti, Emanuele; Hertog, Thomas; Hughes, Scott A.; Jetzer, Philippe; Pani, Paolo; Sotiriou, Thomas P.; Tamanini, Nicola; Witek, Helvi; Yagi, Kent; Yunes, Nicolás; Abdelsalhin, T.; Achucarro, A.; van Aelst, K.; Afshordi, N.; Akcay, S.; Annulli, L.; Arun, K. G.; Ayuso, I.; Baibhav, V.; Baker, T.; Bantilan, H.; Barreiro, T.; Barrera-Hinojosa, C.; Bartolo, N.; Baumann, D.; Belgacem, E.; Bellini, E.; Bellomo, N.; Ben-Dayan, I.; Bena, I.; Benkel, R.; Bergshoefs, E.; Bernard, L.; Bernuzzi, S.; Bertacca, D.; Besancon, M.; Beutler, F.; Beyer, F.; Bhagwat, S.; Bicak, J.; Biondini, S.; Bize, S.; Blas, D.; Boehmer, C.; Boller, K.; Bonga, B.; Bonvin, C.; Bosso, P.; Bozzola, G.; Brax, P.; Breitbach, M.; Brito, R.; Bruni, M.; Brügmann, B.; Bulten, H.; Buonanno, A.; Burko, L. M.; Burrage, C.; Cabral, F.; Calcagni, G.; Caprini, C.; Cárdenas-Avendaño, A.; Celoria, M.; Chatziioannou, K.; Chernoff, D.; Clough, K.; Coates, A.; Comelli, D.; Compère, G.; Croon, D.; Cruces, D.; Cusin, G.; Dalang, C.; Danielsson, U.; Das, S.; Datta, S.; de Boer, J.; De Luca, V.; De Rham, C.; Desjacques, V.; Destounis, K.; Di Filippo, F.; Dima, A.; Dimastrogiovanni, E.; Dolan, S.; Doneva, D.; Duque, F.; Durrer, R.; East, W.; Easther, R.; Elley, M.; Ellis, J. R.; Emparan, R.; Ezquiaga, J. M.; Fairbairn, M.; Fairhurst, S.; Farmer, H. F.; Fasiello, M. R.; Ferrari, V.; Ferreira, P. G.; Ficarra, G.; Figueras, P.; Fisenko, S.; Foffa, S.; Franchini, N.; Franciolini, G.; Fransen, K.; Frauendiener, J.; Frusciante, N.; Fujita, R.; Gair, J.; Ganz, A.; Garcia, P.; Garcia-Bellido, J.; Garriga, J.; Geiger, R.; Geng, C.; Gergely, L. Á.; Germani, C.; Gerosa, D.; Giddings, S. B.; Gourgoulhon, E.; Grandclement, P.; Graziani, L.; Gualtieri, L.; Haggard, D.; Haino, S.; Halburd, R.; Han, W. -B; Hawken, A. J.; Hees, A.; Heng, I. S.; Hennig, J.; Herdeiro, C.; Hervik, S.; Holten, J. v.; Hoyle, C. J. D.; Hu, Y.; Hull, M.; Ikeda, T.; Isi, M.; Jenkins, A.; Julié, F.; Kajfasz, E.; Kalaghatgi, C.; Kaloper, N.; Kamionkowski, M.; Karas, V.; Kastha, S.; Keresztes, Z.; Kidder, L.; Kimpson, T.; Klein, A.; Klioner, S.; Kokkotas, K.; Kolesova, H.; Kolkowitz, S.; Kopp, J.; Koyama, K.; Krishnendu, N. V.; Kroon, J. A. V.; Kunz, M.; Lahav, O.; Landragin, A.; Lang, R. N.; Le Poncin-Lafitte, C.; Lemos, J.; Li, B.; Liberati, S.; Liguori, M.; Lin, F.; Liu, G.; Lobo, F. S. N.; Loll, R.; Lombriser, L.; Lovelace, G.; Macedo, R. P.; Madge, E.; Maggio, E.; Maggiore, M.; Marassi, S.; Marcoccia, P.; Markakis, C.; Martens, W.; Martinovic, K.; Martins, C. J. A. P.; Maselli, A.; Mastrogiovanni, S.; Matarrese, S.; Matas, A.; Mavromatos, N. E.; Mazumdar, A.; Meerburg, P. D.; Megias, E.; Miller, J.; Mimoso, J. P.; Mittnacht, L.; Montero, M. M.; Moore, B.; Martin-Moruno, P.; Musco, I.; Nakano, H.; Nampalliwar, S.; Nardini, G.; Nielsen, A.; Novák, J.; Nunes, N. J.; Okounkova, M.; Oliveri, R.; Oppizzi, F.; Orlando, G.; Oshita, N.; Pappas, G.; Paschalidis, V.; Peiris, H.; Peloso, M.; Perkins, S.; Pettorino, V.; Pikovski, Igor; Pilo, L.; Podolsky, J.; Pontzen, A.; Prabhat, S.; Pratten, G.; Prokopec, T.; Prouza, M.; Qi, H.; Raccanelli, A.; Rajantie, A.; Randall, L.; Raposo, G.; Raymond, V.; Renaux-Petel, S.; Ricciardone, A.; Riotto, A.; Robson, T.; Roest, D.; Rollo, R.; Rosofsky, S.; Ruan, J. J.; Rubiera-García, D.; Ruiz, M.; Rusu, M.; Sabatie, F.; Sago, N.; Sakellariadou, M.; Saltas, I. D.; Sberna, L.; Sathyaprakash, B.; Scheel, M.; Schmidt, P.; Schutz, B.; Schwaller, P.; Shao, L.; Shapiro, S. L.; Shoemaker, D.; Silva, A. D.; Simpson, C.; Sopuerta, C. F.; Spallicci, A.; Stefanek, B. A.; Stein, L.; Stergioulas, N.; Stott, M.; Sutton, P.; Svarc, R.; Tagoshi, H.; Tahamtan, T.; Takeda, H.; Tanaka, T.; Tantilian, G.; Tasinato, G.; Tattersall, O.; Teukolsky, S.; Tiec, A. L.; Theureau, G.; Trodden, M.; Tolley, A.; Toubiana, A.; Traykova, D.; Tsokaros, A.; Unal, C.; Unnikrishnan, C. S.; Vagenas, E. C.; Valageas, P.; Vallisneri, M.; Van den Brand, J.; Van Den Broeck, C.; van de Meent, M.; Vanhove, P.; Varma, V.; Veitch, J.; Vercnocke, B.; Verde, L.; Vernieri, D.; Vernizzi, F.; Vicente, R.; Vidotto, F.; Visser, M.; Vlah, Z.; Vretinaris, S.; Völkel, S.; Wang, Q.; Wang, Yu-Tong; Werner, M. C.; Westernacher, J.; Weygaert, R. v. d.; Wiltshire, D.; Wiseman, T.; Wolf, P.; Wu, K.; Yamada, K.; Yang, H.; Yi, L.; Yue, X.; Yvon, D.; Zilhão, M.; Zimmerman, A.; Zumalacarregui, M.
Abstract: In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the very broad range of topics that might be relevant to LISA,we present here a sample of what we view as particularly promising fundamental physics directions. We organize these directions through a "science-first" approach that allows us to classify how LISA data can inform theoretical physics in a variety of areas. For each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. The classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics.

ID: 157760
Type: article
Authors: Moschou, Sofia-Paraskevi; Vlahakis, Nektarios; Drake, Jeremy J.; Evans, Nancy Remage; Neilson, Hilding R.; Guzik, Joyce Ann; Zuhone, John
Abstract: Cepheids are pulsating variable stars with a periodic chromospheric response at UV wavelengths close to their minimum radius phase. Recently, an X-ray variable signature was captured in observations during the maximum radius phase. This X-ray emission came as a surprise and is not understood. In this work, we use the modern astrophysical code PLUTO to investigate the effects of pulsations on Cepheid X-ray emission. We run a number of hydrodynamic numerical simulations with a variety of initial and boundary conditions in order to explore the capability of shocks to produce the observed phase-dependent X-ray behavior. Finally, we use the Simulated Observations of X-ray Sources (SOXS) package to create synthetic spectra for each simulation case and link our simulations to observables. We show that, for certain conditions, we can reproduce observed X-ray fluxes at phases 0.4-0.8 when the Cepheid is at maximum radius. Our results span a wide range of mass-loss rates, 2 × 10^-13 M_☉ yr^-1 to 3 × 10^-8 M_☉ yr^-1, and peak X-ray luminosities, 5 × 10^-17 erg cm^-2 s^-1 to 1.4 × 10^-12 erg cm^-2 s^-1. We conclude that Cepheids exhibit two-component emission with (a) shock waves being responsible for the phase-dependent variable emission (phases 0.2-0.6) and (b) a separate quiescent mechanism being the dominant emission mechanism for the remaining phases.

ID: 157761
Type: article
Authors: Cohen, Ofer; Garraffo, Cecilia; Moschou, Sofia-Paraskevi; Drake, Jeremy J.; Alvarado-Gómez, J. D.; Glocer, Alex; Fraschetti, Federico
Abstract: We investigate the space environment conditions near the Earth-size planet TOI 700 d using a set of numerical models for the stellar corona and wind, the planetary magnetosphere, and the planetary ionosphere. We drive our simulations using a scaled-down stellar input and a scaled-up solar input in order to obtain two independent solutions. We find that for the particular parameters used in our study, the stellar wind conditions near the planet are not very extreme-slightly stronger than that near the Earth in terms of the stellar wind ram pressure and the intensity of the interplanetary magnetic field. Thus, the space environment near TOI 700 d may not be extremely harmful to the planetary atmosphere, assuming the planet resembles the Earth. Nevertheless, we stress that the stellar input parameters and the actual planetary parameters are unconstrained, and different parameters may result in a much greater effect on the atmosphere of TOI 700 d. Finally, we compare our results to solar wind measurements in the solar system and stress that modest stellar wind conditions may not guarantee atmospheric retention of exoplanets.

ID: 157762
Type: article
Authors: Gronoff, G.; Arras, P.; Baraka, S.; Bell, J. M.; Cessateur, G.; Cohen, O.; Curry, S. M.; Drake, Jeremy J.; Elrod, M.; Erwin, J.; Garcia-Sage, K.; Garraffo, Cecilia; Glocer, A.; Heavens, N. G.; Lovato, K.; Maggiolo, R.; Parkinson, C. D.; Simon Wedlund, C.; Weimer, D. R.; Moore, W. B.
Abstract: The habitability of the surface of any planet is determined by a complex evolution of its interior, surface, and atmosphere. The electromagnetic and particle radiation of stars drive thermal, chemical, and physical alteration of planetary atmospheres, including escape. Many known extrasolar planets experience vastly different stellar environments than those in our solar system: It is crucial to understand the broad range of processes that lead to atmospheric escape and evolution under a wide range of conditions if we are to assess the habitability of worlds around other stars. One problem encountered between the planetary and the astrophysics communities is a lack of common language for describing escape processes. Each community has customary approximations that may be questioned by the other, such as the hypothesis of H-dominated thermosphere for astrophysicists or the Sun-like nature of the stars for planetary scientists. Since exoplanets are becoming one of the main targets for the detection of life, a common set of definitions and hypotheses are required. We review the different escape mechanisms proposed for the evolution of planetary and exoplanetary atmospheres. We propose a common definition for the different escape mechanisms, and we show the important parameters to take into account when evaluating the escape at a planet in time. We show that the paradigm of the magnetic field as an atmospheric shield should be changed and that recent work on the history of Xenon in Earth's atmosphere gives an elegant explanation to its enrichment in heavier isotopes: the so-called Xenon paradox.

ID: 157763
Type: article
Authors: Ligterink, Niels F. W.; El-Abd, Samer J.; Brogan, Crystal L.; Hunter, Todd R.; Remijan, Anthony J.; Garrod, Robin T.; McGuire, Brett
Abstract: Amide molecules produced in space could play a key role in the formation of biomolecules on a young planetary object. However, the formation and chemical network of amide molecules in space is not well understood. In this work, Atacama Large Millimeter/submillimeter Array observations are used to study a number of amide(-like) molecules toward the high-mass star-forming region NGC 6334I. The first detections of cyanamide (NH₂CN), acetamide (CH₃C(O)NH₂), and N-methylformamide (CH₃NHCHO) are presented for this source. These are combined with analyses of isocyanic acid (HNCO) and formamide (NH₂CHO), and a tentative detection of urea (carbamide; NH₂C(O)NH₂). Abundance correlations show that most amides are likely formed in related reactions occurring in ices on interstellar dust grains in NGC 6334I. However, in an expanded sample of sources, large abundance variations are seen for NH₂CN that seem to depend on the source type, which suggests that the physical conditions within the source heavily influence the production of this species. The rich amide inventory of NGC 6334I strengthens the case that interstellar molecules can contribute to the emergence of biomolecules on planets.

ID: 157764
Type: article
Authors: Kaltenegger, Lisa; MacDonald, Ryan J.; Kozakis, Thea; Lewis, Nikole K.; Mamajek, Eric E.; McDowell, Jonathan C.; Vanderburg, Andrew
Abstract: The near-term search for life beyond the solar system currently focuses on transiting planets orbiting small M dwarfs, and the challenges of detecting signs of life in their atmospheres. However, planets orbiting white dwarfs (WDs) would provide a unique opportunity to characterize rocky worlds. The discovery of the first transiting giant planet orbiting a WD, WD 1856+534, showed that planetary-mass objects can survive close-in orbits around WDs. The large radius ratio between WD planets and their host renders them exceptional targets for transmission spectroscopy. Here, we explore the molecular detectability and atmospheric characterization potential for a notional Earth-like planet, evolving in the habitable zone of WD 1856+534, with the James Webb Space Telescope (JWST). We establish that the atmospheric composition of such Earth-like planets orbiting WDs can be precisely retrieved with JWST. We demonstrate that robust >5σ detections of H₂O and CO₂ can be achieved in a five-transit reconnaissance program, while the biosignatures O₃ + CH₄ and CH₄ + N₂O can be detected to >4σ in as few as 25 transits. N₂ and O₂ can be detected to >5σ within 100 transits. Given the short transit duration of WD habitable zone planets (∼2 minutes for WD 1856+534), conclusive molecular detections can be achieved in a small or medium JWST transmission spectroscopy program. Rocky planets in the WD habitable zone therefore represent a promising opportunity to characterize terrestrial planet atmospheres and explore the possibility of a second genesis on these worlds.

ID: 157765
Type: article
Authors: Kuo, C. Y.; Braatz, J. A.; Impellizzeri, C. M. V.; Gao, F.; Pesce, Dominic W.; Reid, Mark J.; Condon, J.; Kamali, F.; Henkel, C.; Greene, J. E.
Abstract: We present very long baseline interferometry (VLBI) images and kinematics of water maser emission in three active galaxies: NGC 5728, Mrk 1, and IRAS 08452-0011. IRAS 08452-0011, at a distance of ∼200 Mpc, is a triple-peaked H₂O megamaser, consistent with a Keplerian rotating disc, indicating a black hole mass of (3.3 $\pm 0.2)\times 10^{7}\, \mathrm{ M}_{\odot }$ . NGC 5728 and Mrk 1 display double-peaked spectra, and VLBI imaging reveals complicated gas kinematics that do not allow for a robust determination of black hole mass. We show evidence that the masers in NGC 5728 are in a wind while the Mrk 1 maser system has both disc and outflow components. We also find that disturbed morphology and kinematics are a ubiquitous feature of all double-peaked maser systems, implying that these maser sources may reside in environments where active galactic nucleus (AGN) winds are prominent at ∼1 pc scale and have significant impact on the masing gas. Such AGNs tend to have black hole masses $M_{\rm BH}\, \lt$ 8 × 10⁶ M_☉ and Eddington ratios $\lambda _{\rm Edd}\, \gtrsim$ 0.1, while the triple-peaked megamasers show an opposite trend.

ID: 157766
Type: article
Authors: Broderick, Avery E.; Pesce, Dominic W.; Tiede, Paul; Pu, Hung-Yi; Gold, Roman
Abstract: Generating images from very long baseline interferometric observations poses a difficult, and generally not unique, inversion problem. This problem is simplified by the introduction of constraints, some generic (e.g., positivity of the intensity) and others motivated by physical considerations (e.g., smoothness, instrument resolution). It is further complicated by the need to simultaneously address instrumental systematic uncertainties and sparse coverage in the u-v plane. We report a new Bayesian image reconstruction technique in the parameter estimation framework THEMIS that has been developed for the Event Horizon Telescope. This has two key features: first, the full Bayesian treatment of the image reconstruction makes it possible to generate a full posterior for the images, permitting a rigorous and quantitative investigation into the statistical significance of image features. Second, it is possible to seamlessly incorporate directly modeled features simultaneously with image reconstruction. We demonstrate this second capability by incorporating a narrow, slashed ring in reconstructions of simulated M87 data in an attempt to detect and characterize the photon ring. We show that it is possible to obtain high-fidelity photon ring sizes, enabling mass measurements with accuracies of 2%-5% that are essentially insensitive to astrophysical uncertainties, and creating opportunities for precision tests of general relativity.

ID: 157767
Type: article
Authors: Torres, Guillermo; Melis, Carl; Kraus, Adam L.; Dupuy, Trent J.; Chilcote, Jeffrey K.; Crepp, Justin R.
Abstract: We report our long-term spectroscopic monitoring of the Pleiades member HII-2147, which was previously spatially resolved at radio wavelengths in very long baseline interferometry (VLBI) observations. It has also been claimed to be a (presumably short-period) double-lined spectroscopic binary with relatively sharp lines, although no orbit has ever been published. Examination of our new spectroscopic material and the historical radial velocities shows that the current and previous spectra are best interpreted as featuring only a single set of lines of a moderately rapidly rotating star with slowly variable radial velocity, which is one of the sources detected by VLBI. We combine our own and other velocities with the VLBI measurements and new adaptive optics observations to derive the first astrometric-spectroscopic orbit of the G5 + G9 pair, with a period of 18.18 ± 0.11 yr. We infer dynamical masses of 0.897 ± 0.022 M_☉ for the spectroscopically visible star and 0.978 ± 0.024 M_☉ for the other, along with a distance of ${136.78}_{-0.46}^{+0.50}$ pc. The lack of detection of the lines of the more massive component in our spectra can be adequately explained if it is rotating much more rapidly than the star we see. This is consistent with the observation that the lines of the secondary are shallower than expected for a star of its spectral type.

ID: 157768
Type: article
Authors: Maxted, P. F. L.; Gaulme, Patrick; Graczyk, D.; Hełminiak, K. G.; Johnston, C.; Orosz, Jerome A.; Prša, Andrej; Southworth, John; Torres, Guillermo; Davies, Guy R.; Ball, Warrick; Chaplin, William J.
Abstract: Accurate masses and radii for normal stars derived from observations of detached eclipsing binary stars are of fundamental importance for testing stellar models and may be useful for calibrating free parameters in these model if the masses and radii are sufficiently precise and accurate. We aim to measure precise masses and radii for the stars in the bright eclipsing binary AI Phe, and to quantify the level of systematic error in these estimates. We use several different methods to model the Transiting Exoplanet Survey Satellite (TESS) light curve of AI Phe combined with spectroscopic orbits from multiple sources to estimate precisely the stellar masses and radii together with robust error estimates. We find that the agreement between different methods for the light-curve analysis is very good but some methods underestimate the errors on the model parameters. The semi-amplitudes of the spectroscopic orbits derived from spectra obtained with modern échelle spectrographs are consistent to within 0.1 per cent. The masses of the stars in AI Phe are $M_1 = 1.1938 \pm 0.0008\, \rm M_{\odot }$ and $M_2 = 1.2438 \pm 0.0008\, \rm M_{\odot }$ , and the radii are $R_1 = 1.8050 \pm 0.0022\, \rm R_{\odot }$ and $R_2 = 2.9332 \pm 0.0023\, \rm R_{\odot }$ . We conclude that it is possible to measure accurate masses and radii for stars in bright eclipsing binary stars to a precision of 0.2 per cent or better using photometry from TESS and spectroscopy obtained with modern échelle spectrographs. We provide recommendations for publishing masses and radii of eclipsing binary stars at this level of precision.

ID: 157769
Type: article
Authors: Torres, Guillermo; Vanderburg, Andrew; Curtis, Jason L.; Kraus, Adam L.; Rizzuto, Aaron C.; Ireland, Michael J.
Abstract: Spectroscopic observations are reported for the 2.75 day, double-lined, detached eclipsing binary EPIC 219552514 located at the turnoff of the old nearby open cluster Ruprecht 147. A joint analysis of our radial-velocity measurements and the K2 light curve leads to masses of ${M}_{1}={1.509}_{-0.056}^{+0.063}\,{M}_{\odot }$ and ${M}_{2}={0.649}_{-0.014}^{+0.015}\,{M}_{\odot }$ for the primary and secondary, along with radii of ${R}_{1}={2.505}_{-0.031}^{+0.026}\,{R}_{\odot }$ and ${R}_{2}={0.652}_{-0.012}^{+0.013}\,{R}_{\odot }$ , respectively. The effective temperatures are 6180 ± 100 K for the F7 primary and 4010 ± 170 K for the late K secondary. The orbit is circular, and the stars' rotation appears to be synchronized with the orbital motion. This is the third eclipsing system analyzed in the same cluster, following our earlier studies of EPIC 219394517 and EPIC 219568666. By comparison with stellar evolution models from the PARSEC series, we infer an age of ${2.67}_{-0.55}^{+0.39}$ Gyr that is consistent with the estimates for the other two systems. EPIC 219552514 is a hierarchical triple system, with the period of the slightly eccentric outer orbit being 463 days. The unseen tertiary is either a low-mass M dwarf or a white dwarf.

ID: 157770
Type: article
Authors: Teske, Johanna; Díaz, Matías R.; Luque, Rafael; Močnik, Teo; Seidel, Julia V.; Otegi, Jon Fernández; Feng, Fabo; Jenkins, James S.; Pallè, Enric; Ségransan, Damien; Udry, Stèphane; Collins, Karen A.; Eastman, Jason D.; Ricker, George R.; Vanderspek, Roland; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Anderson, David R.; Barclay, Thomas; Bouchy, François; Burt, Jennifer A.; Butler, R. Paul; Caldwell, Douglas A.; Collins, Kevin I.; Crane, Jeffrey D.; Dorn, Caroline; Flowers, Erin; Haldemann, Jonas; Helled, Ravit; Hellier, Coel; Jensen, Eric L. N.; Kane, Stephen R.; Law, Nicholas; Lissauer, Jack J.; Mann, Andrew W.; Marmier, Maxime; Nielsen, Louise Dyregaard; Rose, Mark E.; Shectman, Stephen A.; Shporer, Avi; Torres, Guillermo; Wang, Sharon X.; Wolfgang, Angie; Wong, Ian; Ziegler, Carl
Abstract: The Transiting Exoplanet Survey Satellite mission was designed to find transiting planets around bright, nearby stars. Here, we present the detection and mass measurement of a small, short-period (≍4 days) transiting planet around the bright (V = 7.9), solar-type star HD 86226 (TOI-652, TIC 22221375), previously known to host a long-period (∼1600 days) giant planet. HD 86226c (TOI-652.01) has a radius of 2.16 ± 0.08 R_⊕ and a mass of ${7.25}_{-1.12}^{+1.19}$ M_⊕, based on archival and new radial velocity data. We also update the parameters of the longer-period, not-known-to-transit planet, and find it to be less eccentric and less massive than previously reported. The density of the transiting planet is 3.97 g cm^-3, which is low enough to suggest that the planet has at least a small volatile envelope, but the mass fractions of rock, iron, and water are not well-constrained. Given the host star brightness, planet period, and location of the planet near both the "radius gap" and the "hot Neptune desert," HD 86226c is an interesting candidate for transmission spectroscopy to further refine its composition. ^* This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

ID: 157771
Type: article
Authors: Bouma, L. G.; Winn, J. N.; Ricker, G. R.; Vanderspek, R.; Latham, David W.; Seager, S.; Jenkins, J. M.; Barclay, T.; Collins, Karen A.; Doty, J. P.; Louie, D. R.; Quinn, Samuel N.; Rose, M. E.; Smith, J. C.; Villaseñor, J.; Wohler, B.
Abstract: PTFO 8-8695 (CVSO 30) is a star in the 7-10 million year old Orion OB1a cluster that shows brightness dips that resemble planetary transits. Although strong evidence against the planet hypothesis has been presented, the possibility remains debated in the literature. To obtain further clues, we inspected data from the NASA Transiting Exoplanet Survey Satellite (TESS) and the ESA Gaia mission. The Gaia data suggest that PTFO 8-8695 is a binary: the photometric data show it to be overluminous with respect to members of its kinematic group, and the astrometric data are inconsistent with a single star. The TESS light curve shows two different photometric periods. The variability is dominated by a sinusoidal signal with a period of 11.98 hr, presumably caused by stellar rotation. Also present is a 10.76 hr signal consisting of a not-quite sinusoid interrupted by hour-long dips, the type of signal previously interpreted as planetary transits. The phase of the dips is nearly 180° away from the phase of the originally reported dips. As noted previously, this makes them difficult to explain as planetary transits. Instead, we believe that PTFO 8-8695 is a pair of young and rapidly rotating M dwarfs, one of which shows the same "transient-dipper" behavior that has been seen in at least five other cases. The origin of these transient dips is still unknown but likely involves circumstellar material.

ID: 157772
Type: article
Authors: Nielsen, L. D.; Brahm, R.; Bouchy, F.; Espinoza, N.; Turner, O.; Rappaport, S.; Pearce, L.; Ricker, G.; Vanderspek, R.; Latham, David W.; Seager, S.; Winn, J. N.; Jenkins, J. M.; Acton, J. S.; Bakos, G.; Barclay, T.; Barkaoui, K.; Bhatti, W.; Briceño, C.; Bryant, E. M.; Burleigh, M. R.; Ciardi, D. R.; Collins, K. A.; Collins, K. I.; Cooke, B. F.; Csubry, Z.; dos Santos, L. A.; Eigmüller, Ph; Fausnaugh, M. M.; Gan, T.; Gillon, M.; Goad, M. R.; Guerrero, N.; Hagelberg, J.; Hart, R.; Henning, T.; Huang, C. X.; Jehin, E.; Jenkins, J. S.; Jordán, A.; Kielkopf, J. F.; Kossakowski, D.; Lavie, B.; Law, N.; Lendl, M.; de Leon, J. P.; Lovis, C.; Mann, A. W.; Marmier, M.; McCormac, J.; Mori, M.; Moyano, M.; Narita, N.; Osip, D.; Otegi, J. F.; Pepe, F.; Pozuelos, F. J.; Raynard, L.; Relles, Howard M.; Sarkis, P.; Ségransan, D.; Seidel, J. V.; Shporer, A.; Stalport, M.; Stockdale, C.; Suc, V.; Tamura, M.; Tan, T. G.; Tilbrook, R. H.; Ting, E. B.; Trifonov, T.; Udry, S.; Vanderburg, A.; Wheatley, P. J.; Wingham, G.; Zhan, Z.; Ziegler, C.
Abstract: We report the confirmation and mass determination of three hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HIP 65Ab (TOI-129, TIC-201248411) is an ultra-short-period Jupiter orbiting a bright (V = 11.1 mag) K4-dwarf every 0.98 days. It is a massive 3.213 ± 0.078 M_J planet in a grazing transit configuration with an impact parameter of b = 1.17_-0.08^+0.10. As a result the radius is poorly constrained, 2.03_-0.49^+0.61R_J. The planet's distance to its host star is less than twice the separation at which it would be destroyed by Roche lobe overflow. It is expected to spiral into HIP 65A on a timescale ranging from 80 Myr to a few gigayears, assuming a reduced tidal dissipation quality factor of Q_s^' = 10⁷ - 10⁹. We performed a full phase-curve analysis of the TESS data and detected both illumination- and ellipsoidal variations as well as Doppler boosting. HIP 65A is part of a binary stellar system, with HIP 65B separated by 269 AU (3.95 arcsec on sky). TOI-157b (TIC 140691463) is a typical hot Jupiter with a mass of 1.18 ± 0.13 M_J and a radius of 1.29 ± 0.02 R_J. It has a period of 2.08 days, which corresponds to a separation of just 0.03 AU. This makes TOI-157 an interesting system, as the host star is an evolved G9 sub-giant star (V = 12.7). TOI-169b (TIC 183120439) is a bloated Jupiter orbiting a V = 12.4 G-type star. It has a mass of 0.79 ±0.06 M_J and a radius of 1.09_-0.05^+0.08R_J. Despite having the longest orbital period (P = 2.26 days) of the three planets, TOI-169b receives the most irradiation and is situated on the edge of the Neptune desert. All three host stars are metal rich with [Fe / H] ranging from 0.18 to0.24.

ID: 157773
Type: article
Authors: Bluhm, P.; Luque, R.; Espinoza, N.; Pallé, E.; Caballero, J. A.; Dreizler, S.; Livingston, J. H.; Mathur, S.; Quirrenbach, A.; Stock, S.; Van Eylen, V.; Nowak, G.; López, E. D.; Csizmadia, Sz; Zapatero Osorio, M. R.; Schöfer, P.; Lillo-Box, J.; Oshagh, M.; González-Álvarez, E.; Amado, P. J.; Barrado, D.; Béjar, V. J. S.; Cale, B.; Chaturvedi, P.; Cifuentes, C.; Cochran, W. D.; Collins, Karen A.; Collins, K. I.; Cortés-Contreras, M.; Díez Alonso, E.; El Mufti, M.; Ercolino, A.; Fridlund, M.; Gaidos, E.; García, R. A.; Georgieva, I.; González-Cuesta, L.; Guerra, P.; Hatzes, A. P.; Henning, Th; Herrero, E.; Hidalgo, D.; Isopi, G.; Jeffers, S. V.; Jenkins, J. M.; Jensen, E. L. N.; Kábath, P.; Kaminski, A.; Kemmer, J.; Korth, J.; Kossakowski, D.; Kürster, M.; Lafarga, M.; Mallia, F.; Montes, D.; Morales, J. C.; Morales-Calderón, M.; Murgas, F.; Narita, N.; Passegger, V. M.; Pedraz, S.; Persson, C. M.; Plavchan, P.; Rauer, H.; Redfield, S.; Reffert, S.; Reiners, A.; Ribas, I.; Ricker, G. R.; Rodríguez-López, C.; Santos, A. R. G.; Seager, S.; Schlecker, M.; Schweitzer, A.; Shan, Y.; Soto, M. G.; Subjak, J.; Tal-Or, L.; Trifonov, T.; Vanaverbeke, S.; Vanderspek, R.; Wittrock, J.; Zechmeister, M.; Zohrabi, F.
Abstract: We report the confirmation of a transiting planet around the bright weakly active M0.5 V star TOI-1235 (TYC 4384-1735-1, V ≈ 11.5 mag), whose transit signal was detected in the photometric time series of sectors 14, 20, and 21 of the TESS space mission. We confirm the planetary nature of the transit signal, which has a period of 3.44 d, by using precise RV measurements with the CARMENES, HARPS-N, and iSHELL spectrographs, supplemented by high-resolution imaging and ground-based photometry. A comparison of the properties derived for TOI-1235 b with theoretical models reveals that the planet has a rocky composition, with a bulk density slightly higher than that of Earth. In particular, we measure a mass of M_p = 5.9 ± 0.6 M_⊕ and a radius of R_p = 1.69 ± 0.08 R_⊕, which together result in a density of ρ_p = 6.7_{- 1.1}^{+ 1.3} g cm^-3. When compared with other well-characterized exoplanetary systems, the particular combination of planetary radius and mass places our discovery in the radius gap, which is a transition region between rocky planets and planets with significant atmospheric envelopes. A few examples of planets occupying the radius gap are known to date. While the exact location of the radius gap for M dwarfs is still a matter of debate, our results constrain it to be located at around 1.7 R_⊕ or larger at the insolation levels received by TOI-1235 b (~60 S_⊕). This makes it an extremely interesting object for further studies of planet formation and atmospheric evolution.

ID: 157774
Type: article
Authors: Zhang, Congyao; Churazov, Eugene; Dolag, Klaus; Forman, William R.; Zhuravleva, Irina
Abstract: Two Mpc-size contact discontinuities have recently been identified in the XMM-Newton and Suzaku X-ray observations in the outskirts of the Perseus cluster (Walker et al.). These structures have been tentatively interpreted as 'sloshing cold fronts', which are customarily associated with differential motions of the cluster gas, perturbed by a merger. In this study, we consider an alternative scenario, namely, that the most prominent discontinuity, near the cluster virial radius, is the result of the collision between the accretion shock and a 'runaway' merger shock. We also discuss the possible origin of the second discontinuity at ${\sim}1.2{\rm \, Mpc}$ .

ID: 157775
Type: article
Authors: Zhang, Congyao; Churazov, Eugene; Dolag, Klaus; Forman, William R.; Zhuravleva, Irina
Abstract: Several types/classes of shocks naturally arise during formation and evolution of galaxy clusters. One such class is represented by accretion shocks, associated with deceleration of infalling baryons. Such shocks, characterized by a very high Mach number, are present even in 1D models of cluster evolution. Another class is composed of 'runaway merger shocks', which appear when a merger shock, driven by a sufficiently massive infalling subcluster, propagates away from the main-cluster centre. We argue that, when the merger shock overtakes the accretion shock, a new long-living shock is formed that propagates to large distances from the main cluster (well beyond its virial radius), affecting the cold gas around the cluster. We refer to these structures as Merger-accelerated Accretion shocks (MA-shocks) in this paper. We show examples of such MA-shocks in one-dimensioanal (1D) and three-dimensional (3D) simulations and discuss their characteristic properties. In particular, (1) MA-shocks shape the boundary separating the hot intracluster medium (ICM) from the unshocked gas, giving this boundary a 'flower-like' morphology. In 3D, MA-shocks occupy space between the dense accreting filaments. (2) Evolution of MA-shocks highly depends on the Mach number of the runaway merger shock and the mass accretion rate parameter of the cluster. (3) MA-shocks may lead to the misalignment of the ICM boundary and the splashback radius.

ID: 157776
Type: article
Authors: Grazian, A.; Giallongo, E.; Fiore, F.; Boutsia, K.; Civano, Francesca; Cristiani, S.; Cupani, G.; Dickinson, M.; Fontanot, F.; Menci, N.; Romano, M.
Abstract: It is widespread opinion that hydrogen reionization is mainly driven by primeval star-forming galaxies, with high-z active galactic nuclei (AGNs) having a minor role. Recent observations, however, challenge this notion, indicating a number of issues related to a galaxy-driven reionization scenario. We provide here an updated assessment of the space density of relatively faint (M₁₄₅₀ ∼ -22.5) AGNs at z_spec ∼ 5.5 in order to improve the estimate of the photoionization rate contribution from accreting supermassive black holes. Exploiting deep UV rest-frame ground-based spectra collected at the Very Large Telescope on the CANDELS/GOODS-South field and deep Chandra X-ray images in the CANDELS/GOODS-North and EGS areas, we find two relatively bright (M₁₄₅₀ ∼ -22.5) AGNs at z_spec ∼ 5.5. We derive an AGN space density of Φ = 1.29 × 10^-6 cMpc^-3 at z ∼ 5.5 and M₁₄₅₀ ∼ -22.5 by simply dividing their observed number by the cosmological volume in the range 5.0 ∼ -22.5 by simply dividing their observed number by the cosmological volume in the range 5.0 5, in contrast with previous claims mostly based on standard color selection, possibly affected by significant incompleteness. Our estimate for the AGN photoionization rate at z ∼ 5.5 is in agreement with the observed values at similar redshifts, which are needed to keep the intergalactic medium highly ionized. Upcoming James Webb Space Telescope and giant ground-based telescopes observations will improve the study of high-z AGNs and their contribution to the reionization of the universe.

ID: 157643
Type: article
Authors: Fetherolf, Tara; Reddy, Naveen A.; Shapley, Alice E.; Kriek, Mariska; Siana, Brian; Coil, Alison L.; Mobasher, Bahram; Freeman, William R.; Sanders, Ryan L.; Price, Sedona H.; Shivaei, Irene; Azadi, Mojegan; de Groot, Laura; Leung, Gene C. K.; Zick, Tom O.
Abstract: We use a sample of 350 star-forming galaxies at 1.25 ₁₆₀-band alone, we introduce a modified Voronoi binning method that additionally incorporates the S/N distribution of several resolved filters. The spectral energy distribution (SED)-derived resolved E(B - V)_stars, stellar population ages, star-formation rates (SFRs), and stellar masses that are inferred from the Voronoi bins constructed from multiple filters are generally consistent with the properties inferred from the integrated photometry within the uncertainties, with the exception of the inferred E(B - V)_stars from our z ∼ 1.5 sample due to their UV slopes being unconstrained by the resolved photometry. The results from our multifilter Voronoi binning technique are compared to those derived from a 'traditional' single-filter Voronoi binning approach. We find that single-filter binning produces inferred E(B - V)_stars that are systematically redder by 0.02 mag, on average, but could differ by up to 0.20 mag and could be attributed to poorly constrained resolved photometry covering the UV slope. Overall, we advocate that our methodology produces more reliable SED-derived parameters due to the best-fitting resolved SEDs being better constrained at all resolved wavelengths - particularly those covering the UV slope.

ID: 157644
Type: article
Authors: Shivaei, Irene; Reddy, Naveen; Rieke, George; Shapley, Alice; Kriek, Mariska; Battisti, Andrew; Mobasher, Bahram; Sanders, Ryan; Fetherolf, Tara; Azadi, Mojegan; Coil, Alison L.; Freeman, William R.; de Groot, Laura; Leung, Gene; Price, Sedona H.; Siana, Brian; Zick, Tom
Abstract: We derive a UV-optical stellar dust attenuation curve of galaxies at z = 1.4-2.6 as a function of gas-phase metallicity. We use a sample of 218 star-forming galaxies, excluding those with very young or heavily obscured star formation, from the MOSFIRE Deep Evolution Field survey with Hα, Hβ, and [N II]λ 6585 spectroscopic measurements. We constrain the shape of the attenuation curve by comparing the average flux densities of galaxies sorted into bins of dust obscuration using Balmer decrements, i.e., Hα-to-Hβ luminosities. The average attenuation curve for the high-metallicity sample ( $12+\mathrm{log}({\rm{O}}/{\rm{H}})\gt 8.5$ , corresponding to ${M}_{* }\gtrsim {10}^{10.4}$ ${M}_{\odot }$ ) has a shallow slope, identical to that of the Calzetti local starburst curve, and a significant UV 2175 Å extinction bump that is ∼0.5× the strength of the Milky Way bump. On the other hand, the average attenuation curve of the low-metallicity sample ( $12+\mathrm{log}({\rm{O}}/{\rm{H}})\sim 8.2-8.5$ ) has a steeper slope similar to that of the SMC curve, only consistent with the Calzetti slope at the 3σ level. The UV bump is not detected in the low-metallicity curve, indicating the relative lack of the small dust grains causing the bump at low metallicities. Furthermore, we find that on average the nebular reddening (E(B - V)) is a factor of 2 times larger than that of the stellar continuum for galaxies with low metallicities, while the nebular and stellar reddening are similar for galaxies with higher metallicities. The latter is likely due to a high surface density of dusty clouds embedding the star-forming regions but also reddening the continuum in the high-metallicity galaxies.

ID: 157645
Type: article
Authors: Williams, Brian J.; Katsuda, Satoru; Cumbee, Renata; Petre, Robert; Raymond, John C.; Uchida, Hiroyuki
Abstract: We present results from XMM-Newton/Reflection Grating Spectrometer (RGS) observations of prominent knots in the southernmost portion of Tycho's supernova remnant, known to be the remnant of a Type Ia supernova in 1572 C.E. By dispersing the photons from these knots out of the remnant with very little emission in front of or behind them, we obtained the nearly uncontaminated spectra of the knots. In the southernmost knot, the RGS successfully resolved numerous emission lines from Si, Ne, O Heα and Lyα, and Fe L-shell. This is the first clear detection of O lines in Tycho's supernova remnant. Line broadening was measured to be ∼3 eV for the O Heα and ∼4.5 eV for the Fe L lines. If we attribute the broadening to pure thermal Doppler effects, then we obtain kT_O and kT_Fe to be ∼400 keV and 1.5 MeV, respectively. These temperatures can be explained by heating in a reverse shock with a shock velocity of ∼3500 km s^-1. The abundances obtained from fitting the RGS and MOS data together imply substantially elevated amounts of these materials, confirming previous studies that the knots are heated by a reverse shock, and thus contain ejecta material from the supernova. We are unable to find a Type Ia explosion model that reproduces these abundances, but this is likely the result of this knot being too small to extrapolate to the entire remnant.

ID: 157646
Type: article
Authors: Trueba, Nicolas; Miller, J. M.; Fabian, A. C.; Kaastra, J.; Kallman, T.; Lohfink, A.; Proga, D.; Raymond, John; Reynolds, C.; Reynolds, M.; Zoghbi, A.
Abstract: The very small accretion disks in ultracompact X-ray binaries are special laboratories in which to study disk accretion and outflows. We report on three sets of new (250 ks total) and archival (50 ks) Chandra/HETG observations of the "dipping" neutron star X-ray binary 4U 1916-053, which has an orbital period of P ≃ 50 minutes. We find that the bulk of the absorption in all three spectra originates in a disk atmosphere that is redshifted by v ≃ 220-290 km s^-1, corresponding to the gravitational redshift at a radius of R ∼ 1200 GM/c². This shift is present in the strongest, most highly ionized lines (Si XIV and Fe XXVI), with a significance of 5σ. Absorption lines observed during dipping events (typically associated with the outermost disk) instead display no velocity shifts and serve as a local standard of rest, suggesting that the redshift is intrinsic to an inner disk atmosphere and not due to radial motion in the galaxy or a kick. In two spectra, there is also evidence of a more strongly redshifted component that would correspond to a disk atmosphere at R ∼ 70 GM/c²; this component is significant at the 3σ level. Finally, in one spectrum, we find evidence of a disk wind with a blueshift of $v=-{1700}_{-1200}^{+1700}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . If real, this wind would require magnetic driving.

ID: 157647
Type: article
Authors: Ye, Jing; Cai, Qiangwei; Shen, Chengcai; Raymond, John C.; Lin, Jun; Roussev, Ilia I.; Mei, Zhixing
Abstract: Magnetohydrodynamic turbulence is ubiquitous in the process of solar eruptions, and it is crucial for the fast release of energy and the formation of complex thermal structures that have been found in observations. In this paper, we focus on the turbulence in two specific regions: inside the current sheet (CS) and above the flare loops, considering the standard flare model. The gravitationally stratified solar atmosphere is used in MHD simulations, which include the Lundquist number of S = 10⁶, thermal conduction, and radiative cooling. The numerical results are generally consistent with previous simulation work, especially the thermal structures and reconnection rate in flare phases. We can observe the formation of multiple termination shocks (TSs) as well as plasmoid collisions, which make the region above the loop-top more turbulent and heat plasmas to the higher temperature. The spectrum studies show that the property of the MHD turbulence inside the CS is anisotropic, while it is quasi-isotropic above the loop-top. The magnetic spectrum becomes softer when the plasmoids interact with the multiple TSs. Meanwhile, synthetic images and light curves of the Solar Dynamics Observatory/Atmospheric Imaging Assembly 94, 131, 171, 304, and 193 Å channels show intermittent radiation enhancement by turbulence above the loop-top. The spectrum study of the radiation intensity in these five wavelengths gives quite different power indices at the same time. In particular, quasiperiodic pulsations (QPPs) in the turbulent region above the loop-top are investigated, and we also confirm that the heating for plasmas via turbulence is an important contributor to the source of QPPs.

ID: 157648
Type: article
Authors: Koo, Bon-Chul; Kim, Hyun-Jeong; Lee, Yong-Hyun; Raymond, John C.; Lee, Jae-Joon; Yoon, Sung-Chul; Moon, Dae-Sik

ID: 157649
Type: article
Authors: Smith, Randall; Hahn, Michael; Raymond, John; Kallman, T.; Ballance, C. P.; Polito, Vanessa; Del Zanna, Giulio; Gu, Liyi; Hell, Natalie; Cumbee, Renata; Betancourt-Martinez, Gabriele; Costantini, Elisa; Corrales, Lia
Abstract: Cosmic EUV/x-ray spectroscopists, including both solar and astrophysical analysts, have a wide range of high-resolution and high-sensitivity tools in use and a number of new facilities in development for launch. As this bandpass requires placing the spectrometer beyond the Earth's atmosphere, each mission represents a major investment by a national space agency such as NASA, ESA, or JAXA, and more typically a collaboration between two or three. In general justifying new mission requires an improvement in capabilities of at least an order of magnitude, but the sensitivity of these existing missions are already taxing existing atomic data quantity and accuracy. This roadmap reviews the existing missions, showing how in a number of areas atomic data limits the science that can be performed. The missions that will be launched in the coming Decade will without doubt require both more and improved measurements of wavelengths and rates, along with theoretical calculations of collisional and radiative cross sections for a wide range of processes.

ID: 157650
Type: article
Authors: Fesen, Robert A.; Weil, Kathryn E.; Raymond, John C.; Huet, Laurent; Rusterholz, Martin; di Cicco, Dennis; Mittelman, David; Walker, Sean; Drechsler, Marcel; Faworski, Sheldon
Abstract: Wide-field H α images of the Galactic plane have revealed a new supernova remnant (SNR) nearly 3 deg in diameter centred at l = 107.0, b = +9.0. Deep and higher resolution H α and [O III] 5007 Å images show dozens of H α filaments along the remnant's northern, western, and southwestern limbs, but few [O III] bright filaments. The nebula is well detected in the H α Virginia Tech Spectral-Line Survey images, with many of its brighter filaments even visible on Digital Sky Survey images. Low-dispersion spectra of several filaments show either Balmer dominated, non-radiative filaments, or the more common SNR radiative filaments with [S II]/H α ratios above 0.5, consistent with shock-heated line emission. Emission line ratios suggest shock velocities ranging from ≤70 km s^-1 along its western limb to ≃ 100 km s^-1 along its northwestern boundary. While no associated X-ray emission is seen in ROSAT images, faint 1420 MHz radio emission appears coincident with its western and northern limbs. Based on an analysis of the remnant's spatially resolved H α and [O III] emissions, we estimate the remnant's distance at ∼1.5-2.0 kpc implying a physically large (dia. = 75-100 pc) and old (90-110 × 10³ yr) SNR in its post-Sedov radiative phase of evolution expanding into a low-density interstellar medium (n₀ = 0.05-0.2 cm^-3) and lying some 250-300 pc above the Galactic plane.

ID: 157651
Type: article
Authors: Kenyon, Scott J.; Bromley, Benjamin C.
Abstract: We consider whether equilibrium size distributions from collisional cascades match the frequency of impactors derived from New Horizons crater counts on Charon. Using an analytic model and a suite of numerical simulations, we demonstrate that collisional cascades generate wavy size distributions; the morphology of the waves depends on the binding energy of solids ${Q}_{D}^{\star }$ and the collision velocity v_c. For an adopted minimum size of solids, ${r}_{\min }$ = 1 μm, and collision velocity v_c = 1-3 km s^-1, the waves are rather insensitive to the gravitational component of ${Q}_{D}^{\star }$ . If the bulk strength component of ${Q}_{D}^{\star }$ is ${Q}_{s}{r}^{{e}_{s}}$ for particles with radius r, size distributions with small Q_s are much wavier than those with large Q_s; systems with e_s ≍ -0.4 have stronger waves than systems with e_s ≍ 0. Detailed comparisons with the New Horizons data suggest that a collisional cascade among solids with a bulk strength intermediate between weak ice and normal ice produces size distributions fairly similar to that of impactors on Charon. If the surface density Σ of the protosolar nebula varies with semimajor axis a as Σ ≍ 30 g cm^-2 (a/1 au)^-3/2, the timescale for a cascade to generate an approximate equilibrium is 100-300 Myr at 45 au and 10-30 Myr at 25 au. Although it is necessary to perform more complete evolutionary calculations of the Kuiper Belt, collisional cascades are a viable model for producing the size distribution of solids that impacted Charon throughout its history.

ID: 157652
Type: article
Authors: Bromley, Benjamin C.; Kenyon, Scott J.
Abstract: We consider a scenario where the small satellites of Pluto and Charon grew within a disk of debris from an impact between Charon and a trans-Neptunian object (TNO). After Charon's orbital motion boosts the debris into a disk-like structure, rapid orbital damping of meter-sized or smaller objects is essential to prevent the subsequent reaccretion or dynamical ejection by the binary. From analytical estimates and simulations of disk evolution, we estimate an impactor radius of 30-100 km; smaller (larger) radii apply to an oblique (direct) impact. Although collisions between large TNOs and Charon are unlikely today, they were relatively common within the first 0.1-1 Gyr of the solar system. Compared to models where the small satellites agglomerate in the debris left over by the giant impact that produced the Pluto-Charon binary planet, satellite formation from a later impact on Charon avoids the destabilizing resonances that sweep past the satellites during the early orbital expansion of the binary.

ID: 157653
Type: article
Authors: Woolley, Thomas; Matteini, Lorenzo; Horbury, Timothy S.; Bale, Stuart D.; Woodham, Lloyd D.; Laker, Ronan; Alterman, Benjamin L.; Bonnell, John W.; Case, Anthony W.; Kasper, Justin C.; Klein, Kristopher G.; Martinović, Mihailo M.; Stevens, Michael
Abstract: During Parker Solar Probe's first two orbits, there are widespread observations of rapid magnetic field reversals known as switchbacks. These switchbacks are extensively found in the near-Sun solar wind, appear to occur in patches, and have possible links to various phenomena such as magnetic reconnection near the solar surface. As switchbacks are associated with faster plasma flows, we questioned whether they are hotter than the background plasma and whether the microphysics inside a switchback is different to its surroundings. We have studied the reduced distribution functions from the Solar Probe Cup instrument and considered time periods with markedly large angular deflections to compare parallel temperatures inside and outside switchbacks. We have shown that the reduced distribution functions inside switchbacks are consistent with a rigid velocity space rotation of the background plasma. As such, we conclude that the proton core parallel temperature is very similar inside and outside of switchbacks, implying that a temperature-velocity (T-V) relationship does not hold for the proton core parallel temperature inside magnetic field switchbacks. We further conclude that switchbacks are consistent with Alfvénic pulses travelling along open magnetic field lines. The origin of these pulses, however, remains unknown. We also found that there is no obvious link between radial Poynting flux and kinetic energy enhancements suggesting that the radial Poynting flux is not important for the dynamics of switchbacks.

ID: 157654
Type: article
Authors: Cohen, C. M. S.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; Desai, M. I.; Giacalone, J.; Hill, M. E.; Joyce, C. J.; Labrador, A. W.; Leske, R. A.; Matthaeus, W. H.; McComas, D. J.; McNutt, R. L., Jr.; Mewaldt, R. A.; Mitchell, D. G.; Rankin, J. S.; Roelof, E. C.; Schwadron, N. A.; Stone, E. C.; Szalay, J. R.; Wiedenbeck, M. E.; Allen, R. C.; Ho, G. C.; Jian, L. K.; Lario, D.; Odstrcil, D.; Bale, S. D.; Badman, S. T.; Pulupa, M.; MacDowall, R. J.; Kasper, Justin C.; Case, Anthony W.; Korreck, Kelly E.; Larson, D. E.; Livi, Roberto; Stevens, Michael L.; Whittlesey, Phyllis
Abstract: The Parker Solar Probe was launched on 2018 August 12 and completed its second orbit on 2019 June 19 with perihelion of 35.7 solar radii. During this time, the Energetic Particle Instrument-Hi (EPI-Hi, one of the two energetic particle instruments comprising the Integrated Science Investigation of the Sun, IS☉IS) measured seven proton intensity increases associated with stream interaction regions (SIRs), two of which appear to be occurring in the same region corotating with the Sun. The events are relatively weak, with observed proton spectra extending to only a few MeV and lasting for a few days. The proton spectra are best characterized by power laws with indices ranging from -4.3 to -6.5, generally softer than events associated with SIRs observed at 1 au and beyond. Helium spectra were also obtained with similar indices, allowing He/H abundance ratios to be calculated for each event. We find values of 0.016-0.031, which are consistent with ratios obtained previously for corotating interaction region events with fast solar wind ≤600 km s^-1. Using the observed solar wind data combined with solar wind simulations, we study the solar wind structures associated with these events and identify additional spacecraft near 1 au appropriately positioned to observe the same structures after some corotation. Examination of the energetic particle observations from these spacecraft yields two events that may correspond to the energetic particle increases seen by EPI-Hi earlier.

ID: 157655
Type: article
Authors: Ricarte, Angelo; Prather, Ben S.; Wong, George N.; Narayan, Ramesh; Gammie, Charles; Johnson, Michael D.
Abstract: Faraday rotation has been seen at millimeter wavelengths in several low-luminosity active galactic nuclei, including Event Horizon Telescope (EHT) targets M87* and Sgr A*. The observed rotation measure (RM) probes the density, magnetic field, and temperature of material integrated along the line of sight. To better understand how accretion disc conditions are reflected in the RM, we perform polarized radiative transfer calculations using a set of general relativistic magnetohydrodynamic (GRMHD) simulations appropriate for M87*. We find that in spatially resolved millimetre wavelength images on event horizon scales, the RM can vary by orders of magnitude and even flip sign. The observational consequences of this spatial structure include significant time-variability, sign-flips, and non-λ² evolution of the polarization plane. For some models, we find that internal RM can cause significant bandwidth depolarization even across the relatively narrow fractional bandwidths observed by the EHT. We decompose the linearly polarized emission in these models based on their RM and find that emission in front of the mid-plane can exhibit orders of magnitude less Faraday rotation than emission originating from behind the mid-plane or within the photon ring. We confirm that the spatially unresolved (i.e. image integrated) RM is a poor predictor of the accretion rate, with substantial scatter stemming from time variability and inclination effects. Models can be constrained with repeated observations to characterize time variability and the degree of non-λ² evolution of the polarization plane.

ID: 157656
Type: article
Authors: Lada, Charles J.; Dame, Thomas M.
Abstract: We use two existing molecular cloud catalogs derived from the same CO survey and two catalogs derived from local dust extinction surveys to investigate the nature of the giant molecular cloud (GMC) mass-size relation in the Galaxy. We find that the four surveys are well described by M_GMC ∼ R², implying a constant mean surface density, ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ , for the cataloged clouds. However, the scaling coefficients and scatter differ significantly between the CO- and extinction-derived relations. We find that the additional scatter seen in the CO relations is due to a systematic variation in ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ with Galactic radius that is unobservable in the local extinction data. We decompose this radial variation of ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ into two components, a linear negative gradient with Galactic radius and a broad peak coincident with the molecular ring and superposed on the linear gradient. We show that the former may be due to a radial dependence of X_CO on metallicity, while the latter likely results from a combination of increased surface densities of individual GMCs and a systematic upward bias in the measurements of ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ due to cloud blending in the molecular ring. We attribute the difference in scaling coefficients between the CO and extinction data to an underestimate of X_CO. We recalibrate the CO observations of nearby GMCs using extinction measurements to find that locally X_CO = 3.6 ± 0.3 × 10²⁰ cm^-2 (K km s^-1)^-1. We conclude that outside the molecular ring, the GMC population of the Galaxy can be described to relatively good precision by a constant ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ of 35 ${M}_{\odot }$ pc^-2.

ID: 157657
Type: article
Authors: Long, Feng; Pinilla, Paola; Herczeg, Gregory J.; Andrews, Sean M.; Harsono, Daniel; Johnstone, Doug; Ragusa, Enrico; Pascucci, Ilaria; Wilner, David J.; Hendler, Nathan; Jennings, Jeff; Liu, Yao; Lodato, Giuseppe; Menard, Francois; van de Plas, Gerrit; Dipierro, Giovanni
Abstract: We present new Atacama Large Millimeter/submillimeter Array observations for three protoplanetary disks in Taurus at 2.9 mm and comparisons with previous 1.3 mm data both at an angular resolution of ∼0"1 (15 au for the distance of Taurus). In the single-ring disk DS Tau, double-ring disk GO Tau, and multiring disk DL Tau, the same rings are detected at both wavelengths, with radial locations spanning from 50 to 120 au. To quantify the dust emission morphology, the observed visibilities are modeled with a parametric prescription for the radial intensity profile. The disk outer radii, taken as 95% of the total flux encircled in the model intensity profiles, are consistent at both wavelengths for the three disks. Dust evolution models show that dust trapping in local pressure maxima in the outer disk could explain the observed patterns. Dust rings are mostly unresolved. The marginally resolved ring in DS Tau shows a tentatively narrower ring at the longer wavelength, an observational feature expected from efficient dust trapping. The spectral index (α_mm) increases outward and exhibits local minima that correspond to the peaks of dust rings, indicative of the changes in grain properties across the disks. The low optical depths (τ ∼ 0.1-0.2 at 2.9 mm and 0.2-0.4 at 1.3 mm) in the dust rings suggest that grains in the rings may have grown to millimeter sizes. The ubiquitous dust rings in protoplanetary disks modify the overall dynamics and evolution of dust grains, likely paving the way toward the new generation of planet formation.

ID: 157658
Type: article
Authors: Huang, Jane; Andrews, Sean M.; Dullemond, Cornelis P.; Isella, Andrea; Pérez, Laura M.; Guzmán, Viviana V.; Öberg, Karin I.; Zhu, Zhaohuan; Zhang, Shangjia; Bai, Xue-Ning; Benisty, Myriam; Birnstiel, Tilman; Carpenter, John M.; Hughes, A. Meredith; Ricci, Luca; Weaver, Erik; Wilner, David J.

ID: 157659
Type: article
Authors: Huang, Jane; Andrews, Sean M.; Öberg, Karin I.; Ansdell, Megan; Benisty, Myriam; Carpenter, John M.; Isella, Andrea; Pérez, Laura M.; Ricci, Luca; Williams, Jonathan P.; Wilner, David J.; Zhu, Zhaohuan
Abstract: While protoplanetary disks often appear to be compact and well organized in millimeter continuum emission, CO spectral line observations are increasingly revealing complex behavior at large distances from the host star. We present deep Atacama Large Millimeter/submillimeter Array maps of the J = 2-1 transition of ¹²CO, ¹³CO, and C¹⁸O, as well as the J = 3-2 transition of DCO⁺, toward the T Tauri star RU Lup at a resolution of ∼0.3″ (∼50 au). The CO isotopologue emission traces four major components of the RU Lup system: a compact Keplerian disk with a radius of ∼120 au, a non-Keplerian "envelope-like" structure surrounding the disk and extending to ∼260 au from the star, at least five blueshifted spiral arms stretching up to 1000 au, and clumps outside the spiral arms located up to 1500 au in projection from RU Lup. We comment on potential explanations for RU Lup's peculiar gas morphology, including gravitational instability, accretion of material onto the disk, or perturbation by another star. RU Lup's extended non-Keplerian CO emission, elevated stellar accretion rate, and unusual photometric variability suggest that it could be a scaled-down Class II analog of the outbursting FU Ori systems.

ID: 157660
Type: article
Authors: Bergner, Jennifer B.; Öberg, Karin I.; Bergin, Edwin A.; Andrews, Sean M.; Blake, Geoffrey A.; Carpenter, John M.; Cleeves, L. Ilsedore; Guzmán, Viviana V.; Huang, Jane; Jørgensen, Jes K.; Qi, Chunhua; Schwarz, Kamber R.; Williams, Jonathan P.; Wilner, David J.
Abstract: The volatile composition of a planet is determined by the inventory of gas and ice in the parent disk. The volatile chemistry in the disk is expected to evolve over time, though this evolution is poorly constrained observationally. We present Atacama Large Millimeter/submillimeter Array observations of C¹⁸O, C₂H, and the isotopologues H¹³CN, HC¹⁵N, and DCN toward five Class 0/I disk candidates. Combined with a sample of 14 Class II disks presented in Bergner et al., this data set offers a view of volatile chemical evolution over the disk lifetime. Our estimates of C¹⁸O abundances are consistent with a rapid depletion of CO in the first ∼0.5-1 Myr of the disk lifetime. We do not see evidence that C₂H and HCN formation are enhanced by CO depletion, possibly because the gas is already quite under-abundant in CO. Further CO depletion may actually hinder their production by limiting the gas-phase carbon supply. The embedded sources show several chemical differences compared to the Class II stage, which seem to arise from shielding of radiation by the envelope (impacting C₂H formation and HC¹⁵N fractionation) and sublimation of ices from infalling material (impacting HCN and C¹⁸O abundances). Such chemical differences between Class 0/I and Class II sources may affect the volatile composition of planet-forming material at different stages in the disk lifetime.

ID: 157661
Type: article
Authors: van Terwisga, S. E.; van Dishoeck, E. F.; Mann, R. K.; Di Francesco, J.; van der Marel, N.; Meyer, M.; Andrews, Sean M.; Carpenter, J.; Eisner, J. A.; Manara, C. F.; Williams, J. P.
Abstract: Context. Protoplanetary disks in dense, massive star-forming regions are strongly affected by their environment. How this environmental impact changes over time is an important constraint on disk evolution and external photoevaporation models.
Aims: We characterize the dust emission from 179 disks in the core of the young (0.5 Myr) NGC 2024 cluster. By studying how the disk mass varies within the cluster, and comparing these disks to those in other regions, we aim to determine how external photoevaporation influences disk properties over time.
Methods: Using the Atacama Large Millimeter/submillimeter Array, a 2.9'× 2.9' mosaic centered on NGC 2024 FIR 3 was observed at 225 GHz with a resolution of 0.25″, or ~100 AU. The imaged region contains 179 disks identified at IR wavelengths, seven new disk candidates, and several protostars.
Results: The overall detection rate of disks is 32 ± 4%. Few of the disks are resolved, with the exception of a giant (R = 300 AU) transition disk. Serendipitously, we observe a millimeter flare from an X-ray bright young stellar object (YSO), and resolve continuum emission from a Class 0 YSO in the FIR 3 core. Two distinct disk populations are present: a more massive one in the east, along the dense molecular ridge hosting the FIR 1-5 YSOs, with a detection rate of 45 ± 7%. In the western population, towards IRS 1, only 15 ± 4% of disks are detected.
Conclusions: NGC 2024 hosts two distinct disk populations. Disks along the dense molecular ridge are young (0.2-0.5 Myr) and partly shielded from the far ultraviolet radiation of IRS 2b; their masses are similar to isolated 1-3 Myr old SFRs. The western population is older and at lower extinctions, and may be affected by external photoevaporation from both IRS 1 and IRS 2b. However, it is possible these disks had lower masses to begin with.
Tables 1, 2, and B.1 and FITS figure are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A27

ID: 157662
Type: article
Authors: Ferreira, R. R.; Barbosa, R.; Castro, M.; Guerrero, G.; de Almeida, L.; Boumier, P.; do Nascimento, José-Dias
Abstract: Context. One of the most enigmatic phenomena related to solar activity is the so-called Maunder minimum phase. It consists in the lowest sunspot count ever registered for the Sun and has not been confirmed for other stars to date. Since the spectroscopic observations of stellar activity at the Mount Wilson Observatory, the solar analog HD 43587 has shown a very low and apparently invariant activity level, which makes it a Maunder minimum candidate.
Aims: We aim to analyze the chromospheric activity evolution of HD 43587 and its evolutive status, with the intention of unraveling the reasons for this low and flat activity.
Methods: We used an activity measurements dataset available in the literature, and computed the S-index from HARPS and NARVAL spectra to infer a cycle period. Additionally, we analyzed the CoRoT light curve of HD 43587, and applied gyrochronology and activity calibrations to determine its rotation period. Finally, based on an evolutionary model and the inferred rotation period, we used the EULAG-MHD code to perform global MHD simulations of HD 43587 to get some insight into its dynamo process.
Results: We confirm the almost flat activity profile, with a cycle period P_cyc = 10.44 ± 3.03 yr deduced from the S-index time series, and a long-term trend that might be a period of more than 50 yr. It was impossible to define a rotation period from the light curve, however gyrochronology and activity calibrations allow us to infer an indirect estimate of ^̄P_rot = 22.6 ± 1.9 d. Furthermore, the MHD simulations confirm an oscillatory dynamo with a cycle period in good agreement with the observations and a low level of surface magnetic activity.
Conclusions: We conclude that this object might be experiencing a "natural" decrease in magnetic activity as a consequence of its age. Nevertheless, the possibility that HD 43587 is in a Maunder minimum phase cannot be ruled out.

ID: 157663
Type: article
Authors: Carlos, Marília; Meléndez, Jorge; do Nascimento, José-Dias; Castro, Matthieu
Abstract: We determine lithium (Li) abundances for solar twins in the M67 open cluster to add valuable information about the correlation between Li depletion and stellar age and, then, better understand stellar structure and evolution. We use high resolution and good signal-to-noise ratio spectra to characterize Li depletion in three solar twins from M67, using spectral synthesis in the region of the asymmetric 6707.75 Å Li I feature. The mean Li abundance value of A(Li) = 1.6 ± 0.2 dex for our sample of M67 solar twins (our three stars plus a fourth solar twin from a previous analysis in the literature) presents Li abundance expected for its age. Also, the scatter estimated from the standard deviation of the Li abundances in this work is similar to the typical scatter found in a sample of field solar twins presented in the literature.

ID: 157664
Type: article
Authors: do Nascimento, J. -D, Jr.; de Almeida, L.; Velloso, E. N.; Anthony, F.; Barnes, S. A.; Saar, Steven H.; Meibom, Søren; da Costa, J. S.; Castro, M.; Galarza, J. Y.; Lorenzo-Oliveira, D.; Beck, P. G.; Meléndez, J.
Abstract: A major obstacle to interpreting the rotation period distribution for main-sequence stars from Kepler mission data has been the lack of a precise evolutionary status for these objects. We address this by investigating the evolutionary status based on Gaia Data Release 2 parallaxes and photometry for more than 30,000 Kepler stars with rotation period measurements. Many of these are subgiants and should be excluded in future work on dwarfs. We particularly investigate a 193-star sample of solar analogs and report newly determined rotation periods for 125 of these. These include 54 stars from a prior sample, of which we can confirm the periods for 50. The remainder are new, and 10 of them longer than a solar rotation period, suggesting that Sun-like stars continue to spin down on the main sequence past solar age. Our sample of solar analogs could potentially serve as a benchmark for future missions, such as PLAnetary Transits and Oscillations of stars, and emphasizes the need for additional astrometric, photometric, and spectroscopic information before interpreting the stellar populations and results from time series surveys.

ID: 157665
Type: article
Authors: Dupree, Andrea K.; Strassmeier, Klaus G.; Matthews, Lynn D.; Uitenbroek, Han; Calderwood, Thomas; Granzer, Thomas; Guinan, Edward F.; Leike, Reimar; Montargès, Miguel; Richards, Anita M. S.; Wasatonic, Richard; Weber, Michael
Abstract: The bright supergiant Betelgeuse (Alpha Orionis, HD 39801) experienced a visual dimming during 2019 December and the first quarter of 2020, reaching an historic minimum 2020 February 7-13. During 2019 September-November, prior to the optical dimming event, the photosphere was expanding. At the same time, spatially resolved ultraviolet spectra using the Hubble Space Telescope/Space Telescope Imaging Spectrograph revealed a substantial increase in the ultraviolet spectrum and Mg II line emission from the chromosphere over the southern hemisphere of the star. Moreover, the temperature and electron density inferred from the spectrum and C II diagnostics also increased in this hemisphere. These changes happened prior to the Great Dimming Event. Variations in the Mg II k-line profiles suggest material moved outwards in response to the passage of a pulse or acoustic shock from 2019 September through November. It appears that this extraordinary outflow of material from the star, likely initiated by convective photospheric elements, was enhanced by the coincidence with the outward motions in this phase of the ∼400 day pulsation cycle. These ultraviolet observations appear to provide the connecting link between the known large convective cells in the photosphere and the mass ejection event that cooled to form the dust cloud in the southern hemisphere imaged in 2019 December, and led to the exceptional optical dimming of Betelgeuse in 2020 February.

ID: 157666
Type: article
Authors: Johnson, Christian I.; Dupree, Andrea K.; Mateo, Mario; Bailey, John I.,III; Olszewski, Edward W.; Walker, Matthew G.
Abstract: The most massive and complex globular clusters in the Galaxy are thought to have originated as the nuclear cores of now tidally disrupted dwarf galaxies, but the connection between globular clusters and dwarf galaxies is tenuous with the M54/Sagittarius system representing the only unambiguous link. The globular cluster Omega Centauri (ω Cen) is more massive and chemically diverse than M 54, and is thought to have been the nuclear star cluster of either the Sequoia or Gaia-Enceladus galaxy. Local Group dwarf galaxies with masses equivalent to these systems often host significant populations of very metal-poor stars ([Fe/H] ^∗ This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

ID: 157667
Type: article
Authors: Pawlak, Mariusz; Sadeghpour, Hossein R.
Abstract: We compute the Rydberg spectrum of a single Ca⁺ ion in a Paul trap by incorporating various internal and external coupling terms of the ion to the trap in the Hamiltonian. The coupling terms include spin-orbit coupling in Ca⁺, charge (electron and ionic core) coupling to the radio frequency and static fields, ion-electron coupling in the Paul trap, and ion center-of-mass coupling. The electronic Rydberg states are precisely described by a one-electron model potential for e^-+Ca^{2 +} , and accurate eigenenergies, quantum defect parameters, and static and tensor polarizabilities for a number of excited Rydberg states are obtained. The time-periodic rf Hamiltonian is expanded in the Floquet basis, and the trapping-field-broadened Rydberg lines are compared with recent observations of Ca⁺(23 P ) and Ca⁺(52 F ) Rydberg lines.

ID: 157668
Type: article
Authors: Vrinceanu, Daniel; Onofrio, Roberto; Sadeghpour, Hossein R.
Abstract: Scattering phenomena between charged particles and highly excited Rydberg atoms are of critical importance in many processes in plasma physics and astrophysics. While a Maxwell-Boltzmann (MB) energy distribution for the charged particles is often assumed for calculations of collisional rate coefficients, in this contribution we relax this assumption and use two different energy distributions, a bimodal MB distribution and a $\unicode[STIX]{x1D705}$-distribution. Both variants share a high-energy tails occurring with higher probability than the corresponding MB distribution. The high-energy tail may significantly affect rate coefficients for various processes. We focus the analysis to specific situations by showing the dependence of the rate coefficients on the principal quantum number of hydrogen atoms in $n$-changing collisions with electrons in the excitation and ionization channels and in a temperature range relevant to the divertor region of a tokamak device. We finally discuss the implications for diagnostics of laboratory plasmas.

ID: 157669
Type: article
Authors: Pereira, M. E. S.; Palmese, A.; Varga, T. N.; McClintock, T.; Soares-Santos, M.; Burgad, J.; Annis, J.; Farahi, A.; Lin, H.; Choi, A.; DeRose, J.; Esteves, J.; Gatti, M.; Gruen, D.; Hartley, W. G.; Hoyle, B.; Jeltema, T.; MacCrann, N.; Roodman, A.; Sánchez, C.; Shin, T.; von der Linden, A.; Zuntz, J.; Abbott, T. M. C.; Aguena, M.; Avila, S.; Bertin, E.; Bhargava, S.; Bridle, S. L.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Costanzi, M.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Estrada, J.; Everett, S.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hinton, S. R.; Hollowood, D. L.; Honscheid, K.; James, David J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Lima, M.; Maia, M. A. G.; March, M.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Miquel, R.; Ogando, R. L. C.; Paz-Chinchón, F.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Serrano, S.; Sevilla-Noarbe, I.; Smith, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Wechsler, R. H.; Weller, J.; Zhang, Y.; DES Collaboration
Abstract: We present the weak-lensing mass calibration of the stellar-mass-based μ_⋆ mass proxy for redMaPPer galaxy clusters in the Dark Energy Survey Year 1. For the first time, we are able to perform a calibration of μ_⋆ at high redshifts, z > 0.33. In a blinded analysis, we use ∼6000 clusters split into 12 subsets spanning the ranges 0.1 ≤ z at high redshifts, z > 0.33. In a blinded analysis, we use ∼6000 clusters split into 12 subsets spanning the ranges 0.1 ≤ z _⋆ up to ${\sim} 5.5 \times 10^{13} \, \mathrm{M}_{\odot }$ , and infer the average masses of these subsets through modelling of their stacked weak-lensing signal. In our model, we account for the following sources of systematic uncertainty: shear measurement and photometric redshift errors, miscentring, cluster-member contamination of the source sample, deviations from the Navarro-Frenk-White halo profile, halo triaxiality, and projection effects. We use the inferred masses to estimate the joint mass-μ_⋆-z scaling relation given by $\langle M_{200c} | \mu _{\star },z \rangle = M_0 (\mu _{\star }/5.16\times 10^{12} \, \mathrm{M_{\odot }})^{F_{\mu _{\star }}} ((1+z)/1.35)^{G_z}$ . We find $M_0= (1.14 \pm 0.07) \times 10^{14} \, \mathrm{M_{\odot }}$ with $F_{\mu _{\star }}= 0.76 \pm 0.06$ and G_z = -1.14 ± 0.37. We discuss the use of μ_⋆ as a complementary mass proxy to the well-studied richness λ for: (i) exploring the regimes of low z, λ < 20 and high λ, z ∼ 1; and (ii) testing systematics such as projection effects for applications in cluster cosmology.

ID: 157670
Type: article
Authors: Xue, Ci; Willis, Eric R.; Loomis, Ryan A.; Lee, Kin Long Kelvin; Burkhardt, Andrew M.; Shingledecker, Christopher N.; Charnley, Steven B.; Cordiner, Martin A.; Kalenskii, Sergei; McCarthy, Michael C.; Herbst, Eric; Remijan, Anthony J.; McGuire, Brett A.
Abstract: We report an astronomical detection of HC₄NC for the first time in the interstellar medium with the Green Bank Telescope toward the TMC-1 molecular cloud with a minimum significance of 10.5σ. The total column density and excitation temperature of HC₄NC are determined to be ${3.29}_{-1.20}^{+8.60}\times {10}^{11}$ cm^-2 and ${6.7}_{-0.3}^{+0.3}\ {\rm{K}}$ , respectively, using Markov chain Monte Carlo analysis. In addition to HC₄NC, HCCNC is distinctly detected whereas no clear detection of HC₆NC is made. We propose that the dissociative recombination of the protonated cyanopolyyne, HC₅NH⁺, and the protonated isocyanopolyyne, HC₄NCH⁺, are the main formation mechanisms for HC₄NC while its destruction is dominated by reactions with simple ions and atomic carbon. With the proposed chemical networks, the observed abundances of HC₄NC and HCCNC are reproduced satisfactorily.

ID: 157671
Type: article
Authors: Tadaki, Ken-ichi; Belli, Sirio; Burkert, Andreas; Dekel, Avishai; Förster Schreiber, Natascha M.; Genzel, Reinhard; Hayashi, Masao; Herrera-Camus, Rodrigo; Kodama, Tadayuki; Kohno, Kotaro; Koyama, Yusei; Lee, Minju M.; Lutz, Dieter; Mowla, Lamiya; Nelson, Erica J.; Renzini, Alvio; Suzuki, Tomoko L.; Tacconi, Linda J.; Übler, Hannah; Wisnioski, Emily; Wuyts, Stijn
Abstract: We present 0"2 resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations at 870 μm in a stellar mass-selected sample of 85 massive ( ${M}_{\star }\gt {10}^{11}\,{M}_{\odot }$ ) star-forming galaxies (SFGs) at $z=1.9\mbox{--}2.6$ in the CANDELS/3D-Hubble Space Telescope fields of UDS and GOODS-S. We measure the effective radius of the rest-frame far-infrared (FIR) emission for 62 massive SFGs. They are distributed over wide ranges of FIR size from ${R}_{{\rm{e}},\mathrm{FIR}}=0.4\,\mathrm{kpc}$ to ${R}_{{\rm{e}},\mathrm{FIR}}=6\,\mathrm{kpc}$ . The effective radius of the FIR emission is smaller by a factor of ${2.3}_{-1.0}^{+1.9}$ than the effective radius of the optical emission and is smaller by a factor of ${1.9}_{-1.0}^{+1.9}$ than the half-mass radius. Taking into account potential extended components, the FIR size would change only by ∼10%. By combining the spatial distributions of the FIR and optical emission, we investigate how galaxies change the effective radius of the optical emission and the stellar mass within a radius of 1 kpc, ${M}_{1\mathrm{kpc}}$ . The compact starburst puts most of the massive SFGs on the mass-size relation for quiescent galaxies (QGs) at z ∼ 2 within 300 Myr if the current star formation activity and its spatial distribution are maintained. We also find that within 300 Myr, ∼38% of massive SFGs can reach the central mass of ${M}_{1\mathrm{kpc}}={10}^{10.5}\,{M}_{\odot }$ , which is around the boundary between massive SFGs and QGs. These results suggest an outside-in transformation scenario in which a dense core is formed at the center of a more extended disk, likely via dissipative in-disk inflows. Synchronized observations at ALMA 870 μm and James Webb Space Telescope 3-4 μm will explicitly verify this scenario.

ID: 157672
Type: article
Authors: Weil, Kathryn E.; Fesen, Robert A.; Patnaude, Daniel J.; Milisavljevic, Dan
Abstract: SN 2017eaw, the tenth supernova observed in NGC 6946, was a normal Type II-P supernova with an estimated 11-13 M_☉ red supergiant progenitor. Here we present nebular-phase spectra of SN 2017eaw at +545 and +900 days post-max, extending approximately 50-400 days past the epochs of previously published spectra. While the +545 day spectrum is similar to spectra taken between days +400 and +493, the +900 day spectrum shows dramatic changes both in spectral features and emission-line profiles. The Hα emission is flat-topped and boxlike with sharp blue and red profile velocities of ≃-8000 and +7500 km s^-1. These late-time spectral changes indicate strong circumstellar interaction with a mass-loss shell, expelled ∼1700 yr before explosion. SN 2017eaw's +900 day spectrum is similar to those seen for SN 2004et and SN 2013ej observed 2-3 yr after explosion. We discuss the importance of late-time monitoring of bright SNe II-P and the nature of presupernova mass-loss events for SN II-P evolution.

ID: 157673
Type: article
Authors: Cargile, Phillip A.; Conroy, Charlie; Johnson, Benjamin D.; Ting, Yuan-Sen; Bonaca, Ana; Dotter, Aaron; Speagle, Joshua S.
Abstract: We present MINESweeper, a tool to measure stellar parameters by jointly fitting observed spectra and broadband photometry to model isochrones and spectral libraries. This approach enables the measurement of spectrophotometric distances, in addition to stellar parameters such as T_eff, $\mathrm{log}g$, [Fe/H], [α/Fe], and radial velocity. MINESweeper employs a Bayesian framework and can easily incorporate a variety of priors, including Gaia parallaxes. Mock data are fit in order to demonstrate how the precision of derived parameters depends on evolutionary phase and signal-to-noise ratio. We then fit a selection of data in order to validate the model outputs. Fits to a variety of benchmark stars including Procyon, Arcturus, and the Sun result in derived stellar parameters that are in good agreement with the literature. We then fit combined spectra and photometry of stars in the open and globular clusters M92, M13, M3, M107, M71, and M67. Derived distances, [Fe/H], [α/Fe], and $\mathrm{log}g$-T_eff relations are in overall good agreement with literature values, although there are trends between metallicity and $\mathrm{log}g$ within clusters that point to systematic uncertainties at the ≍0.1 dex level. Finally, we fit a large sample of stars from the H3 Spectroscopic Survey in which high-quality Gaia parallaxes are also available. These stars are fit without the Gaia parallaxes so that the geometric parallaxes can serve as an independent test of the spectrophotometric distances. Comparison between the two reveals good agreement within their formal uncertainties after accounting for the Gaia zero-point uncertainties.

ID: 157674
Type: article
Authors: Naidu, Rohan P.; Conroy, Charlie; Bonaca, Ana; Johnson, Benjamin D.; Ting, Yuan-Sen; Caldwell, Nelson; Zaritsky, Dennis; Cargile, Phillip A.
Abstract: In the ΛCDM paradigm, the Galactic stellar halo is predicted to harbor the accreted debris of smaller systems. To identify these systems, the H3 Spectroscopic Survey, combined with Gaia, is gathering 6D phase-space and chemical information in the distant Galaxy. Here we present a comprehensive inventory of structure within 50 kpc from the Galactic center using a sample of 5684 giants at $| b| \gt 40^\circ $ and $| Z| \gt 2\,\mathrm{kpc}$ . We identify known structures including the high-α disk, the in situ halo (disk stars heated to eccentric orbits), Sagittarius (Sgr), Gaia-Sausage-Enceladus (GSE), the Helmi Streams, Sequoia, and Thamnos. Additionally, we identify the following new structures: (i) Aleph ([Fe/H] = -0.5), a low-eccentricity structure that rises a surprising 10 kpc off the plane, (ii) and (iii) Arjuna ([Fe/H] = -1.2) and I'itoi ([Fe/H] 80% of the halo is built by two massive (M_⋆ ∼ 10⁸-10⁹M_☉) accreted dwarfs: GSE ([Fe/H] = -1.2) within 25 kpc and Sgr ([Fe/H] = -1.0) beyond 25 kpc. This explains the relatively high overall metallicity of the halo ([Fe/H] ≍ -1.2). We attribute ≳95% of the sample to one of the listed structures, pointing to a halo built entirely from accreted dwarfs and heating of the disk.

ID: 157675
Type: article
Authors: Bonaca, Ana; Conroy, Charlie; Cargile, Phillip A.; Naidu, Rohan P.; Johnson, Benjamin D.; Zaritsky, Dennis; Ting, Yuan-Sen; Caldwell, Nelson; Han, Jiwon Jesse; van Dokkum, Pieter
Abstract: The archeological record of stars in the Milky Way opens a uniquely detailed window into the early formation and assembly of galaxies. Here we use 11,000 main-sequence turn-off stars with well-measured ages, $[\mathrm{Fe}/{\rm{H}}]$ , $[\alpha /\mathrm{Fe}]$ , and orbits from the H3 Survey and Gaia to time the major events in the early Galaxy. Located beyond the Galactic plane, $1\lesssim | Z| /\mathrm{kpc}\lesssim 4$ , this sample contains three chemically distinct groups: a low-metallicity population, and low-α and high-α groups at higher metallicity. The age and orbit distributions of these populations show that (1) the high-α group, which includes both disk stars and the in situ halo, has a star formation history independent of eccentricity that abruptly truncated 8.3 ± 0.1 Gyr ago (z ≃ 1); (2) the low-metallicity population, which we identify as the accreted stellar halo, is on eccentric orbits and its star formation truncated $10.2{.}_{-0.1}^{+0.2}$ Gyr ago (z ≃ 2); (3) the low-α population is primarily on low-eccentricity orbits and the bulk of its stars formed less than 8 Gyr ago. These results suggest a scenario in which the Milky Way accreted a satellite galaxy at z ≍ 2 that merged with the early disk by z ≍ 1. This merger truncated star formation in the early high-α disk and perturbed a fraction of that disk onto halo-like orbits. The merger enabled the formation of a chemically distinct, low-α disk at z ≲ 1. The lack of any stars on halo-like orbits at younger ages indicates that this event was the last significant disturbance to the Milky Way disk.

ID: 157676
Type: article
Authors: Price, Ellen M.; Cleeves, L. Ilsedore; Öberg, Karin I.
Abstract: The composition of a protoplanetary disk is set by a combination of interstellar inheritance and gas and grain surface chemical reactions within the disk. The survival of inherited molecules, as well as the disk in situ chemistry depends on the local temperature, density and irradiation environment, which can change over time due to stellar and disk evolution, as well as transport in the disk. We address one aspect of this coupling between the physical and chemical evolution in disks by following accretion streamlines of gas and small grains in the disk midplane, while simultaneously taking the evolving star into account. This approach is computationally efficient and enables us to take into account changing physical conditions without reducing the chemical network. We find that many species are enhanced in the inner disk midplane in the dynamic model due to inward transport of cosmic-ray driven chemical products, resulting in, e.g., orders of magnitude hydrocarbon enhancements at 1 au, compared to a static disk. For several other chemical families, there is no difference between the static and dynamic models, indicative of a robust chemical reset, while yet others show differences between static and dynamic models that depend on complex interactions between physics and chemistry during the inward track. The importance of coupling dynamics and chemistry when modeling the chemical evolution of protoplanetary disks thus depends on what chemistry is of interest.

ID: 157677
Type: article
Authors: Guillet, V.; Girart, J. M.; Maury, Anaëlle J.; Alves, F. O.
Abstract: Context. The azimuthal polarization patterns observed in some protoplanetary disks by the Atacama Large Millimetre Array (ALMA) at millimeter wavelengths have raised doubts about whether they are truly produced by dust grains that are aligned with the magnetic field lines. These conclusions were based on the calculations of dust polarized emission in the Rayleigh regime, that is, for grain sizes that are much smaller than the wavelength. However, the grain size in such disks is typically estimated to be in the range of 0.1-1 mm from independent observations.
Aims: We study the dust polarization properties of aligned grains in emission in the Mie regime, that is, when the mean grain size approaches the wavelength.
Methods: By using the T-MATRIX and DustEM codes, we computed the spectral dependence of the polarization fraction in emission for grains in perfect spinning alignment for various grain size distributions. We restricted our study to weakly-elongated oblate and prolate grains of astrosilicate composition that have a mean size ranging from 10 μm to 1 mm.
Results: In the submillimeter and millimeter wavelength range, the polarization by B-field aligned grains becomes negative for grains larger than ∼250 μm, meaning that the polarization vector becomes parallel to the B-field. The transition from the positive to the negative polarization occurs at a wavelength of λ ∼ 1 mm. The regime of negative polarization does not exist for grains that are smaller than ∼100 μm.
Conclusions: When using realistic grain size distributions for disks with grains up to the submillimeter sizes, the polarization direction of thermal emission by aligned grains is shown to be parallel to the direction of the magnetic field over a significant fraction of the wavelengths typically used to observe young protoplanetary disks. This property may explain the peculiar azimuthal orientation of the polarization vectors in some of the disks observed with ALMA and attest to the conserved ability of dust polarized emission to trace the magnetic field in disks.

ID: 157678
Type: article
Authors: Karkare, K. S.; Barry, P. S.; Bradford, C. M.; Chapman, S.; Doyle, S.; Glenn, J.; Gordon, S.; Hailey-Dunsheath, S.; Janssen, R. M. J.; Kovács, Attila; LeDuc, H. G.; Mauskopf, P.; McGeehan, R.; Redford, J.; Shirokoff, E.; Tucker, C.; Wheeler, J.; Zmuidzinas, J.
Abstract: SuperSpec is an on-chip filter bank spectrometer designed for wideband moderate-resolution spectroscopy at millimeter wavelengths, employing TiN kinetic inductance detectors. SuperSpec technology will enable large-format spectroscopic integral field units suitable for high-redshift line intensity mapping and multi-object spectrographs. In previous results, we have demonstrated noise performance in individual detectors suitable for photon noise-limited ground-based observations at excellent mm-wave sites. In these proceedings, we present the noise performance of a full R ∼275 spectrometer measured using deployment-ready RF hardware and software. We report typical noise equivalent powers through the full device of ∼3 ×10^-16 WHz-1^/2 at expected sky loadings, which are photon noise dominated. Based on these results, we plan to deploy a six-spectrometer demonstration instrument to the Large Millimeter Telescope in early 2020.

ID: 157679
Type: article
Authors: Kovács, Orsolya E.; Bogdán, Ákos; Canning, Rebecca E. A.
Abstract: Ultradiffuse galaxies (UDGs) exhibit low surface brightness, but their optical extent is comparable to that of Milky Way-type galaxies. In this work, we utilize Chandra X-ray observations of 404 UDGs in the Coma cluster and address two crucial goals. First, we constrain the formation scenario of UDGs by probing the X-ray emission originating from diffuse gas and from the population of unresolved low-mass X-ray binaries (LMXBs) residing in globular clusters (GCs). It is expected that both the luminosity of the hot gas and the number of GCs, and hence the luminosity from GC-LMXBs, are proportional to the total mass of the dark matter halo. We do not detect statistically significant emission from the hot gas or from GC-LMXBs. The upper limits on the X-ray luminosities suggest that the bulk of the UDGs reside in low-mass dark matter halos, implying that they are genuine dwarf galaxies. This conclusion agrees with our previous results obtained for isolated UDGs, arguing that UDGs are a homogeneous population of galaxies. Second, we constrain the AGN occupation fraction of UDGs, i.e., the fraction of UDGs that are occupied by an active galactic nucleus, for the first time. To this end, we cross-correlate the position of detected X-ray sources in the Coma cluster with the position of UDGs. We identify two UDGs that have a luminous X-ray source at 3"0 and 3"2 from their center, which could be off-center AGNs. However, Monte Carlo simulations suggest that one of these sources could be the result of spatial coincidence with a background AGN. Therefore, we place an upper limit of ≲0.5% on the AGN occupation fraction of UDGs.

ID: 157680
Type: article
Authors: Němeček, Zdeněk; Ďurovcová, Tereza; Šafránková, Jana; Richardson, John D.; Šimůnek, Jiří; Stevens, Michael L.
Abstract: The solar wind nonradial velocity components observed beyond the Alfvén point are usually attributed to waves, the interaction of different streams, or other transient phenomena. However, Earth-orbiting spacecraft as well as monitors at L1 indicate systematic deviations of the wind velocity from the radial direction. Since these deviations are of the order of several degrees, the calibration of the instruments is often questioned. This paper investigates for the first time the evolution of nonradial components of the solar wind flow along the path from ≍0.17 to 10 au. A comparison of observations at 1 au with those closer to or farther from the Sun based on measurements of many spacecraft at different locations in the heliosphere (Parker Solar Probe, Helios 1 and 2, Wind, Advanced Composition Explorer, Spektr-R, Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) probes, Mars Atmosphere and Volatile Evolution (MAVEN), Voyagers 1 and 2) shows that (I) the average values of nonradial components are not zero and vary in a systematic manner with the distance from the Sun and (II) their values significantly depend on the solar wind radial velocity.

ID: 157681
Type: article
Authors: Bouquin, Daina R.; Chivvis, Daniel A.; Henneken, Edwin; Lockhart, Kelly; Muench, August; Koch, Jennifer
Abstract: Software has been a crucial contributor to scientific progress in astronomy for decades, but practices that enable machine-actionable citations have not been consistently applied to software itself. Instead, software citation behaviors developed independently from standard publication mechanisms and policies, resulting in human-readable citations that remain hidden over time and that cannot represent the influence software has had in the field. These historical software citation behaviors need to be understood in order to improve software citation guidance and develop relevant publishing practices that fully support the astronomy community. To this end, a 23 year retrospective analysis of software citation practices in astronomy was developed. Astronomy publications were mined for 410 aliases associated with nine software packages and analyzed to identify past practices and trends that prevent software citations from benefiting software authors.

ID: 157682
Type: article
Authors: Gall, Amy C.; Dipti; Buechele, S. W.; Sanders, S.; Szabo, C. I.; Silwal, R.; Ralchenko, Yu; Brickhouse, Nancy S.; Takacs, E.
Abstract: Non-thermal electron distributions, such as beams of electrons, are found in many laboratory and astrophysical plasma sources and can produce anisotropic and polarized emission. Theories used to model the emission require sublevel specific analysis, which can be difficult to verify experimentally. Using two polarization-sensitive Johann-type crystal spectrometers at the National Institute of Standards and Technology (NIST) electron beam ion trap facility, we measured the linear polarization of well-known dielectronic recombination satellite transitions from Li-like Ar ions and two blended features from Be-like ions. The spectrometers observed the plasma at 90° relative to the electron beam propagation direction, and the crystal dispersion planes were oriented perpendicular relative to each other to allow for differing polarization sensitivities. Measurements were taken near the resonance energies of each line and compared with theoretical predictions based on relativistic magnetic sublevel atomic kinetics using the density-matrix theory. Most of the predictions are in excellent agreement with measured values.

ID: 157683
Type: article
Authors: Hocdé, V.; Nardetto, N.; Borgniet, S.; Lagadec, E.; Kervella, P.; Mérand, A.; Evans, N.; Gillet, D.; Mathias, Ph; Chiavassa, A.; Gallenne, A.; Breuval, L.; Javanmardi, B.
Abstract: Context. It has recently been shown that the infrared (IR) emission of Cepheids, constant over the pulsation cycle, might be due to a pulsating shell of ionized gas with a radius of about 15% of that of the star radius, which could be attributed to the chromospheric activity of Cepheids.
Aims: The aim of this paper is to investigate the dynamical structure of the chromosphere of Cepheids along the pulsation cycle and to quantify its size.
Methods: We present Hα and calcium near-infrared triplet (Ca IR) profile variations using high-resolution spectroscopy with the UVES spectrograph of a sample of 24 Cepheids with a good period coverage from ≈3 to 60 days. After a qualitative analysis of the spectral line profiles, we quantified the Van Hoof effect (velocity gradient between the Hα and Ca IR) as a function of the period of the Cepheids. We then used the Schwarzschild mechanism (a line doubling due to a shock wave) to quantify the size of the chromosphere.
Results: We find a significant Van Hoof effect for Cepheids with a period larger than P = 10 days. In particular, Hα lines are delayed with a velocity gradient up to ∆v ≈ 30 km s^-1 compared to Ca IR. By studying the shocks, we find that the size of the chromosphere of long-period Cepheids is of at least ≈50% of the stellar radius, which is consistent at first order with the size of the shell made of ionized gas previously found from the analysis of IR excess. Last, for most of the long-period Cepheids in the sample, we report a motionless absorption feature in the Hα line that we attribute to a circumstellar envelope that surrounds the chromosphere.
Conclusions: Analyzing the Ca IR lines of Cepheids is of importance to potentially unbias the period-luminosity relation from their IR excess, particularly in the context of forthcoming observations of radial velocity measurements from the Radial Velocity Spectrometer on board Gaia, which could be sensitive to their chromosphere.
Based on observations made with ESO telescopes at Paranal observatory under program IDs: 098.D-0379(A), 0100.D-0397(A) and 0101.D-0551(A).

ID: 157684
Type: article
Authors: Ma, Jingzhe; Elvis, Martin; Fabbiano, Giuseppina; Baloković, Mislav; Maksym, W. Peter; Jones, Mackenzie L.; Risaliti, Guido
Abstract: The recent Chandra discovery of extended ∼kiloparsec-scale hard (>3 keV) X-ray emission in nearby Compton-thick (CT) active galactic nuclei (AGN) opens a new window to improving AGN torus modeling and investigating how the central supermassive black hole interacts with and impacts the host galaxy. Since there are only a handful of detections so far, we need to establish a statistical sample to determine the ubiquity of the extended hard X-ray emission in CT AGN and quantify the amount and extent of this component. In this paper, we present the spatial analysis results of a pilot Chandra imaging survey of seven nearby ( $0.006\lt z\lt 0.013$ ) CT AGN selected from the Swift-BAT spectroscopic AGN survey. We find that five out of the seven CT AGN show extended emission in the 3-7 keV band detected at >3σ above the Chandra point-spread function (PSF), with ∼12%-22% of the total emission in the extended components. ESO 137-G034 and NGC 3281 display biconical ionization structures with extended hard X-ray emission reaching kiloparsec scales (∼1.9 and 3.5 kpc in diameter). The other three show extended hard X-ray emission above the PSF out to at least ∼360 pc in radius. We find a trend that a minimum 3-7 keV count rate of 0.01 counts s^-1 and total excess fraction >20% are required to detect a prominent extended hard X-ray component. Given that this extended hard X-ray component appears to be relatively common in this uniformly selected CT AGN sample, we further discuss the implications for torus modeling and AGN feedback.

ID: 157685
Type: article
Authors: McGuire, Brett A.; Burkhardt, Andrew M.; Loomis, Ryan A.; Shingledecker, Christopher N.; Lee, Kin Long Kelvin; Charnley, Steven B.; Cordiner, Martin A.; Herbst, Eric; Kalenskii, Sergei; Momjian, Emmanuel; Willis, Eric R.; Xue, Ci; Remijan, Anthony J.; McCarthy, Michael C.
Abstract: We present an overview of the GBT Observations of TMC-1: Hunting Aromatic Molecules Large Program on the Green Bank Telescope. This and a related program were launched to explore the depth and breadth of aromatic chemistry in the interstellar medium at the earliest stages of star formation, following our earlier detection of benzonitrile (c-C₆H₅CN) in TMC-1. In this work, details of the observations, use of archival data, and data reduction strategies are provided. Using these observations, the interstellar detection of propargyl cyanide (HCCCH₂CN) is described, as well as the accompanying laboratory spectroscopy. We discuss these results, and the survey project as a whole, in the context of investigating a previously unexplored reservoir of complex, gas-phase molecules in pre-stellar sources. A series of companion papers describe other new astronomical detections and analyses.

ID: 157686
Type: article
Authors: Rosen, Anna L.; Offner, Stella S. R.; Sadavoy, Sarah I.; Bhandare, Asmita; Vázquez-Semadeni, Enrique; Ginsburg, Adam
Abstract: Star formation is a multi-scale, multi-physics problem ranging from the size scale of molecular clouds (∼10 s pc) down to the size scales of dense prestellar cores (∼0.1 pc) that are the birth sites of stars. Several physical processes like turbulence, magnetic fields and stellar feedback, such as radiation pressure and outflows, are more or less important for different stellar masses and size scales. During the last decade a variety of technological and computing advances have transformed our understanding of star formation through the use of multi-wavelength observations, large scale observational surveys, and multi-physics multi-dimensional numerical simulations. Additionally, the use of synthetic observations of simulations have provided a useful tool to interpret observational data and evaluate the importance of various physical processes on different scales in star formation. Here, we review these recent advancements in both high- (M ≳8 M_☉) and low-mass star formation.

ID: 157687
Type: article
Authors: Zhao, Bo; Tomida, Kengo; Hennebelle, Patrick; Tobin, John J.; Maury, Anaëlle; Hirota, Tomoya; Sánchez-Monge, Álvaro; Kuiper, Rolf; Rosen, Anna L.; Bhandare, Asmita; Padovani, Marco; Lee, Yueh-Ning
Abstract: Recent observations have suggested that circumstellar disks may commonly form around young stellar objects. Although the formation of circumstellar disks can be a natural result of the conservation of angular momentum in the parent cloud, theoretical studies instead show disk formation to be difficult from dense molecular cores magnetized to a realistic level, owing to efficient magnetic braking that transports a large fraction of the angular momentum away from the circumstellar region. We review recent progress in the formation and early evolution of disks around young stellar objects of both low-mass and high-mass, with an emphasis on mechanisms that may bridge the gap between observation and theory, including non-ideal MHD effects and asymmetric perturbations in the collapsing core (e.g., magnetic field misalignment and turbulence). We also address the associated processes of outflow launching and the formation of multiple systems, and discuss possible implications in properties of protoplanetary disks.