Publication Search Results

ID: 159333
Type: article
Authors: Carmichael, Theron W.; Quinn, Samuel N.; Zhou, George; Grieves, Nolan; Irwin, Jonathan M.; Stassun, Keivan G.; Vanderburg, Andrew M.; Winn, Joshua N.; Bouchy, Francois; Brasseur, Clara E.; Briceño, César; Caldwell, Douglas A.; Charbonneau, David; Collins, Karen A.; Colon, Knicole D.; Eastman, Jason D.; Fausnaugh, Michael; Fong, William; Fűrész, Gábor; Huang, Chelsea; Jenkins, Jon M.; Kielkopf, John F.; Latham, David W.; Law, Nicholas; Lund, Michael B.; Mann, Andrew W.; Ricker, George R.; Rodriguez, Joseph E.; Schwarz, Richard P.; Shporer, Avi; Tenenbaum, Peter; Wood, Mackenna L.; Ziegler, Carl
Abstract: We report the discovery of two transiting brown dwarfs (BDs), TOI-811b and TOI-852b, from NASA's Transiting Exoplanet Survey Satellite mission. These two transiting BDs have similar masses but very different radii and ages. Their host stars have similar masses, effective temperatures, and metallicities. The younger and larger transiting BD is TOI-811b at a mass of M_b = 59.9 ± 13.0M_J and radius of R_b = 1.26 ± 0.06R_J, and it orbits its host star in a period of P = 25.16551 ± 0.00004 days. We derive the host star's age of ${93}_{-29}^{+61}$ Myr from an application of gyrochronology. The youth of this system, rather than external heating from its host star, is why this BD's radius is relatively large. This constraint on the youth of TOI-811b allows us to test substellar mass-radius evolutionary models at young ages where the radius of BDs changes rapidly. TOI-852b has a similar mass at M_b = 53.7 ± 1.4M_J but is much older (4 or 8 Gyr, based on bimodal isochrone results of the host star) and is also smaller with a radius of R_b = 0.83 ± 0.04R_J. TOI-852b's orbital period is P = 4.94561 ± 0.00008 days. TOI-852b joins the likes of other old transiting BDs that trace out the oldest substellar mass-radius evolutionary models where contraction of the BD's radius slows and approaches a constant value. Both host stars have a mass of M_⋆ = 1.32M_⊙ ± 0.05 and differ in their radii, T_eff, and [Fe/H], with TOI-811 having R_⋆ = 1.27 ± 0.09R_⊙, T_eff = 6107 ± 77 K, and [Fe/H] = + 0.40 ± 0.09 and TOI-852 having R_⋆ = 1.71 ± 0.04R_⊙, T_eff = 5768 ± 84 K, and [Fe/H] = + 0.33 ± 0.09. We take this opportunity to examine how TOI-811b and TOI-852b serve as test points for young and old substellar isochrones, respectively.

ID: 159336
Type: article
Authors: Daylan, Tansu; Pinglé, Kartik; Wright, Jasmine; Günther, Maximilian N.; Stassun, Keivan G.; Kane, Stephen R.; Vanderburg, Andrew; Jontof-Hutter, Daniel; Rodriguez, Joseph E.; Shporer, Avi; Huang, Chelsea X.; Mikal-Evans, Thomas; Badenas-Agusti, Mariona; Collins, Karen A.; Rackham, Benjamin V.; Quinn, Samuel N.; Cloutier, Ryan; Collins, Kevin I.; Guerra, Pere; Jensen, Eric L. N.; Kielkopf, John F.; Massey, Bob; Schwarz, Richard P.; Charbonneau, David; Lissauer, Jack J.; Irwin, Jonathan M.; Baştürk, Özgür; Fulton, Benjamin; Soubkiou, Abderahmane; Zouhair, Benkhaldoun; Howell, Steve B.; Ziegler, Carl; Briceño, César; Law, Nicholas; Mann, Andrew W.; Scott, Nic; Furlan, Elise; Ciardi, David R.; Matson, Rachel; Hellier, Coel; Anderson, David R.; Butler, R. Paul; Crane, Jeffrey D.; Teske, Johanna K.; Shectman, Stephen A.; Kristiansen, Martti H.; Terentev, Ivan A.; Schwengeler, Hans Martin; Ricker, George R.; Vanderspek, Roland; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Berta-Thompson, Zachory K.; Bouma, Luke G.; Fong, William; Furesz, Gabor; Henze, Christopher E.; Morgan, Edward H.; Quintana, Elisa; Ting, Eric B.; Twicken, Joseph D.
Abstract: We report the discovery and validation of four extrasolar planets hosted by the nearby, bright, Sun-like (G3V) star HD 108236 using data from the Transiting Exoplanet Survey Satellite (TESS). We present transit photometry, reconnaissance, and precise Doppler spectroscopy, as well as high-resolution imaging, to validate the planetary nature of the objects transiting HD 108236, also known as the TESS Object of Interest (TOI) 1233. The innermost planet is a possibly rocky super-Earth with a period of ${3.79523}_{-0.00044}^{+0.00047}$ days and has a radius of 1.586 ± 0.098 R_⊕. The outer planets are sub-Neptunes, with potential gaseous envelopes, having radii of ${2.068}_{-0.091}^{+0.10}$ R_⊕, 2.72 ± 0.11 R_⊕, and ${3.12}_{-0.12}^{+0.13}$ R_⊕ and periods of ${6.20370}_{-0.00052}^{+0.00064}$ days, ${14.17555}_{-0.0011}^{+0.00099}$ days, and ${19.5917}_{-0.0020}^{+0.0022}$ days, respectively. With V and K_s magnitudes of 9.2 and 7.6, respectively, the bright host star makes the transiting planets favorable targets for mass measurements and, potentially, for atmospheric characterization via transmission spectroscopy. HD 108236 is the brightest Sun-like star in the visual (V) band known to host four or more transiting exoplanets. The discovered planets span a broad range of planetary radii and equilibrium temperatures and share a common history of insolation from a Sun-like star (R_⋆ = 0.888 ± 0.017 R_⊙, T_eff = 5730 ± 50 K), making HD 108236 an exciting, opportune cosmic laboratory for testing models of planet formation and evolution.

ID: 158644
Type: article
Authors: Brahm, Rafael; Nielsen, Louise D.; Wittenmyer, Robert A.; Wang, Songhu; Rodriguez, Joseph E.; Espinoza, Néstor; Jones, Matías I.; Jordán, Andrés; Henning, Thomas; Hobson, Melissa; Kossakowski, Diana; Rojas, Felipe; Sarkis, Paula; Schlecker, Martin; Trifonov, Trifon; Shahaf, Sahar; Ricker, George; Vanderspek, Roland; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Addison, Brett C.; Bakos, Gáspár Á.; Bhatti, Waqas; Bayliss, Daniel; Berlind, Perry; Bieryla, Allyson; Bouchy, Francois; Bowler, Brendan P.; Briceño, César; Brown, Timothy M.; Bryant, Edward M.; Caldwell, Douglas A.; Charbonneau, David; Collins, Karen A.; Davis, Allen B.; Esquerdo, Gilbert A.; Fulton, Benjamin J.; Guerrero, Natalia M.; Henze, Christopher E.; Hogan, Aleisha; Horner, Jonathan; Huang, Chelsea X.; Irwin, Jonathan; Kane, Stephen R.; Kielkopf, John; Mann, Andrew W.; Mazeh, Tsevi; McCormac, James; McCully, Curtis; Mengel, Matthew W.; Mireles, Ismael; Okumura, Jack; Plavchan, Peter; Quinn, Samuel N.; Rabus, Markus; Saesen, Sophie; Schlieder, Joshua E.; Segransan, Damien; Shiao, Bernie; Shporer, Avi; Siverd, Robert J.; Stassun, Keivan G.; Suc, Vincent; Tan, Thiam-Guan; Torres, Pascal; Tinney, Chris G.; Udry, Stephane; Vanzi, Leonardo; Vezie, Michael; Vines, Jose I.; Vuckovic, Maja; Wright, Duncan J.; Yahalomi, Daniel A.; Zapata, Abner; Zhang, Hui; Ziegler, Carl
Abstract: We present the discovery of two new 10 day period giant planets from the Transiting Exoplanet Survey Satellite mission, whose masses were precisely determined using a wide diversity of ground-based facilities. TOI-481 b and TOI-892 b have similar radii (0.99 ± 0.01 ${R}_{{\rm{J}}}$ and 1.07 ± 0.02 ${R}_{{\rm{J}}}$ , respectively), and orbital periods (10.3311 days and 10.6266 days, respectively), but significantly different masses (1.53 ± 0.03 ${M}_{{\rm{J}}}$ versus 0.95 ± 0.07 ${M}_{{\rm{J}}}$ , respectively). Both planets orbit metal-rich stars ( $[\mathrm{Fe}/{\rm{H}}]$ = $+0.26\pm 0.05$ dex and $[\mathrm{Fe}/{\rm{H}}]$ = $+0.24\pm 0.05$ for TOI-481 and TOI-892, respectively) but at different evolutionary stages. TOI-481 is a ${M}_{\star }$ = 1.14 ± 0.02 ${M}_{\odot }$ , ${R}_{\star }$ = 1.66 ± 0.02 ${R}_{\odot }$ G-type star ( ${T}_{\mathrm{eff}}$ = $5735\pm 72$ K), that with an age of 6.7 Gyr, is in the turn-off point of the main sequence. TOI-892 on the other hand, is a F-type dwarf star ( ${T}_{\mathrm{eff}}$ = $6261\pm 80$ K), which has a mass of ${M}_{\star }$ = 1.28 ± 0.03 ${M}_{\odot }$ and a radius of ${R}_{\star }$ = 1.39 ± 0.02 ${R}_{\odot }$ . TOI-481 b and TOI-892 b join the scarcely populated region of transiting gas giants with orbital periods longer than 10 days, which is important to constrain theories of the formation and structure of hot Jupiters.

ID: 157584
Type: article
Authors: Cloutier, Ryan; Eastman, Jason D.; Rodriguez, Joseph E.; Astudillo-Defru, Nicola; Bonfils, Xavier; Mortier, Annelies; Watson, Christopher A.; Stalport, Manu; Pinamonti, Matteo; Lienhard, Florian; Harutyunyan, Avet; Damasso, Mario; Latham, David W.; Collins, Karen A.; Massey, Robert; Irwin, Jonathan; Winters, Jennifer G.; Charbonneau, David; Ziegler, Carl; Matthews, Elisabeth; Crossfield, Ian J. M.; Kreidberg, Laura; Quinn, Samuel N.; Ricker, George; Vanderspek, Roland; Seager, Sara; Winn, Joshua; Jenkins, Jon M.; Vezie, Michael; Udry, Stéphane; Twicken, Joseph D.; Tenenbaum, Peter; Sozzetti, Alessandro; Ségransan, Damien; Schlieder, Joshua E.; Sasselov, Dimitar; Santos, Nuno C.; Rice, Ken; Rackham, Benjamin V.; Poretti, Ennio; Piotto, Giampaolo; Phillips, David; Pepe, Francesco; Molinari, Emilio; Mignon, Lucile; Micela, Giuseppina; Melo, Claudio; de Medeiros, José R.; Mayor, Michel; Matson, Rachel A.; Martinez Fiorenzano, Aldo F.; Mann, Andrew W.; Magazzú, Antonio; Lovis, Christophe; López-Morales, Mercedes; Lopez, Eric; Lissauer, Jack J.; Lépine, Sébastien; Law, Nicholas; Kielkopf, John F.; Johnson, John A.; Jensen, Eric L. N.; Howell, Steve B.; Gonzales, Erica; Ghedina, Adriano; Forveille, Thierry; Figueira, Pedro; Dumusque, Xavier; Dressing, Courtney D.; Doyon, René; Díaz, Rodrigo F.; Fabrizio, Luca Di; Delfosse, Xavier; Cosentino, Rosario; Conti, Dennis M.; Collins, Kevin I.; Cameron, Andrew Collier; Ciardi, David; Caldwell, Douglas A.; Burke, Christopher; Buchhave, Lars; Briceño, César; Boyd, Patricia; Bouchy, François; Beichman, Charles; Artigau, Étienne; Almenara, Jose M.
Abstract: We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT 3780 (TIC 36724087, TOI-732, V = 13.07, K_s = 8.204, R_s = 0.374 R_☉, M_s = 0.401 M_☉, d = 22 pc). The two planet candidates are identified in a single Transiting Exoplanet Survey Satellite sector and validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of P_b = 0.77, P_c = 12.25 days and sizes r_p,b = 1.33 ± 0.07, r_p,c = 2.30 ± 0.16 R_⊕, the two planets span the radius valley in period-radius space around low-mass stars, thus making the system a laboratory to test competing theories of the emergence of the radius valley in that stellar mass regime. By combining 63 precise radial velocity measurements from the High Accuracy Radial velocity Planet Searcher (HARPS) and HARPS-N, we measure planet masses of ${m}_{p,b}={2.62}_{-0.46}^{+0.48}$ and ${m}_{p,c}={8.6}_{-1.3}^{+1.6}$ M_⊕, which indicates that LTT 3780b has a bulk composition consistent with being Earth-like, while LTT 3780c likely hosts an extended H/He envelope. We show that the recovered planetary masses are consistent with predictions from both photoevaporation and core-powered mass-loss models. The brightness and small size of LTT 3780, along with the measured planetary parameters, render LTT 3780b and c as accessible targets for atmospheric characterization of planets within the same planetary system and spanning the radius valley.

ID: 157585
Type: article
Authors: Cloutier, Ryan; Rodriguez, Joseph E.; Irwin, Jonathan; Charbonneau, David; Stassun, Keivan G.; Mortier, Annelies; Latham, David W.; Isaacson, Howard; Howard, Andrew W.; Udry, Stéphane; Wilson, Thomas G.; Watson, Christopher A.; Pinamonti, Matteo; Lienhard, Florian; Giacobbe, Paolo; Guerra, Pere; Collins, Karen A.; Beiryla, Allyson; Esquerdo, Gilbert A.; Matthews, Elisabeth; Matson, Rachel A.; Howell, Steve B.; Furlan, Elise; Crossfield, Ian J. M.; Winters, Jennifer G.; Nava, Chantanelle; Ment, Kristo; Lopez, Eric D.; Ricker, George; Vanderspek, Roland; Seager, Sara; Jenkins, Jon M.; Ting, Eric B.; Tenenbaum, Peter; Sozzetti, Alessandro; Sha, Lizhou; Ségransan, Damien; Schlieder, Joshua E.; Sasselov, Dimitar; Roy, Arpita; Robertson, Paul; Rice, Ken; Poretti, Ennio; Piotto, Giampaolo; Phillips, David; Pepper, Joshua; Pepe, Francesco; Molinari, Emilio; Mocnik, Teo; Micela, Giuseppina; Mayor, Michel; Martinez Fiorenzano, Aldo F.; Mallia, Franco; Lubin, Jack; Lovis, Christophe; López-Morales, Mercedes; Kosiarek, Molly R.; Kielkopf, John F.; Kane, Stephen R.; Jensen, Eric L. N.; Isopi, Giovanni; Huber, Daniel; Hill, Michelle L.; Harutyunyan, Avet; Gonzales, Erica; Giacalone, Steven; Ghedina, Adriano; Ercolino, Andrea; Dumusque, Xavier; Dressing, Courtney D.; Damasso, Mario; Dalba, Paul A.; Cosentino, Rosario; Conti, Dennis M.; Colón, Knicole D.; Collins, Kevin I.; Cameron, Andrew Collier; Ciardi, David; Christiansen, Jessie; Chontos, Ashley; Cecconi, Massimo; Caldwell, Douglas A.; Burke, Christopher; Buchhave, Lars; Beichman, Charles; Behmard, Aida; Beard, Corey; Akana Murphy, Joseph M.
Abstract: Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period-radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, ${r}_{{\rm{p}}}={1.738}_{-0.076}^{+0.087}$ ${R}_{\oplus }$ ), a planet whose size and period are intermediate between the competing model predictions, thus making the system an important test case for emergence models of the rocky/nonrocky transition around early M dwarfs (R_s = 0.630 ± 0.015 ${R}_{\odot }$ , M_s = 0.640 ± 0.016 ${M}_{\odot }$ ). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial velocities (RVs) from HARPS-N and HIRES. We measure a planet mass of ${6.91}_{-0.85}^{+0.75}$ ${M}_{\oplus }$ , which implies an iron core mass fraction of ${20}_{-12}^{+15}$ % in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like, and we constrain an H/He envelope mass fraction to be <0.5% at 90% confidence. Our results are consistent with model predictions from thermally driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remains efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin ( $P={21.8}_{-0.8}^{+0.9}$ days, ${m}_{{\rm{p}}}\sin i={13.0}_{-5.3}^{+3.8}$ ${M}_{\oplus }$ ) that cannot be firmly ruled out by our data.

ID: 156330
Type: article
Authors: Gan, Tianjun; Shporer, Avi; Livingston, John H.; Collins, Karen A.; Mao, Shude; Trani, Alessandro A.; Gandolfi, Davide; Hirano, Teruyuki; Luque, Rafael; Stassun, Keivan G.; Ziegler, Carl; Howell, Steve B.; Hellier, Coel; Irwin, Jonathan M.; Winters, Jennifer G.; Anderson, David R.; Briceño, César; Law, Nicholas; Mann, Andrew W.; Bonfils, Xavier; Astudillo-Defru, Nicola; Jensen, Eric L. N.; Anglada-Escudé, Guillem; Ricker, George R.; Vanderspek, Roland; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Furesz, Gabor; Guerrero, Natalia M.; Quintana, Elisa; Twicken, Joseph D.; Caldwell, Douglas A.; Tenenbaum, Peter; Huang, Chelsea X.; Rowden, Pamela; Rojas-Ayala, Bárbara
Abstract: We report the first discovery of a thick-disk planet, LHS 1815b (TOI- 704b, TIC 260004324), detected in the Transiting Exoplanet Survey Satellite (TESS) survey. LHS 1815b transits a bright (V = 12.19 mag, K = 7.99 mag) and quiet M dwarf located 29.87 ± 0.02 pc away with a mass of 0.502 ± 0.015 M_☉ and a radius of 0.501 ± 0.030 R_☉. We validate the planet by combining space- and ground-based photometry, spectroscopy, and imaging. The planet has a radius of 1.088 ± 0.064 R_⊕ with a 3σ mass upper limit of 8.7 M_⊕. We analyze the galactic kinematics and orbit of the host star LHS 1815 and find that it has a large probability (P_thick/P_thin = 6482) to be in the thick disk with a much higher expected maximal height (Z_max = 1.8 kpc) above the Galactic plane compared with other TESS planet host stars. Future studies of the interior structure and atmospheric properties of planets in such systems using, for example, the upcoming James Webb Space Telescope, can investigate the differences in formation efficiency and evolution for planetary systems between different Galactic components (thick disks, thin disks, and halo).

ID: 156364
Type: article
Authors: Kain, Isabel J.; Newton, Elisabeth R.; Dittmann, Jason A.; Irwin, Jonathan M.; Mann, Andrew W.; Thao, Pa Chia; Charbonneau, David; Winters, Jennifer G.
Abstract: The abundance of planets with orbital periods of a few to tens of days suggests that exoplanets experience complex dynamical histories. Planets in young stellar clusters or associations have well-constrained ages and therefore provide an opportunity to explore the dynamical evolution of exoplanets. K2-25b is a Neptune-sized planet in an eccentric, 3.48 day orbit around an M4.5 dwarf star in the Hyades cluster (650 Myr). In order to investigate its non-zero eccentricity and tight orbit, we analyze transit timing variations (TTVs) which could reveal clues to the migration processes that may have acted on the planet. We obtain 12 nonconsecutive transits using the MEarth observatories and long-term photometric monitoring, which we combine with 10 transits from the Spitzer Space Telescope and 20 transits from K2. Tables of MEarth photometry accompany this work. We fit each transit lightcurve independently. We first investigate whether inhomogeneities on the stellar surface (such as spots or plages) are differentially affecting our transit observations. The measured transit depth does not vary significantly between transits, though we see some deviations from the fiducial transit model. We then looked for TTVs as evidence of a nontransiting perturber in the system. We find no evidence for >1 M_⊕ mass companions within a 2:1 period ratio, or for >5 M_⊕ mass planets within a 7:2 period ratio.

ID: 156325
Type: article
Authors: Lamman, Claire; Baranec, Christoph; Berta-Thompson, Zachory K.; Law, Nicholas M.; Schonhut-Stasik, Jessica; Ziegler, Carl; Salama, Maïssa; Jensen-Clem, Rebecca; Duev, Dmitry A.; Riddle, Reed; Kulkarni, Shrinivas R.; Winters, Jennifer G.; Irwin, Jonathan M.
Abstract: We analyze observations from Robo-AO's field M dwarf survey taken on the 2.1 m Kitt Peak telescope and perform a multiplicity comparison with Gaia DR2. Through its laser-guided, automated system, the Robo-AO instrument has yielded the largest adaptive optics M dwarf multiplicity survey to date. After developing an interface to visually identify and locate stellar companions, we selected 11 low-significance Robo-AO detections for follow-up on the Keck II telescope using NIRC2. In the Robo-AO survey we find 553 candidate companions within 4″ around 534 stars out of 5566 unique targets, most of which are new discoveries. Using a position cross-match with DR2 on all targets, we assess the binary recoverability of Gaia DR2 and compare the properties of multiples resolved by both Robo-AO and Gaia. The catalog of nearby M dwarf systems and their basic properties presented here can assist other surveys which observe these stars, such as the NASA TESS mission.

ID: 158738
Type: article
Authors: Medina, Amber A.; Winters, Jennifer G.; Irwin, Jonathan M.; Charbonneau, David
Abstract: We present a study of flare rates, rotation periods, and spectroscopic activity indicators of 125 single stars within 15 parsecs and with masses between 0.1 and 0.3 M_? observed during the first year of the TESS mission, with the goal of elucidating the relationship between these various magnetically connected phenomena. We gathered multiepoch high-resolution spectra of each target, and we measured equivalent widths of the activity indicators helium I D₃, Ha, and the calcium infrared triplet line at 8542.09 Å. We present 18 new rotation periods from MEarth photometry and 19 new rotation periods from TESS photometry. We present a catalog of 1392 flares. After correcting for sensitivity, we find the slope of the flare frequency distribution for all stars to have a standard value of a = 1.98 ± 0.02. We determine R_31.5, the rate of flares per day with energies above E = 3.16 × 10³¹ ergs in the TESS bandpass. We find that below a critical value of Ha EW = -0.71 Å, log R_31.5 increases linearly with increasing Ha emission; above this value, log R_31.5 declines rapidly. The stars divide into two groups: 26% have Ha in emission, high flare rates with typical values of log R_31.5 = -1.30 ± 0.08, and have Rossby numbers = -1.30 ± 0.08, and have Rossby numbers _31.5 < -3.86, with the majority of these stars not showing a single flare during the TESS observations.

ID: 156226
Type: article
Authors: Shporer, Avi; Collins, Karen A.; Astudillo-Defru, Nicola; Irwin, Jonathan; Bonfils, Xavier; Collins, Kevin I.; Matthews, Elisabeth; Winters, Jennifer G.; Anderson, David R.; Armstrong, James D.; Charbonneau, David; Cloutier, Ryan; Daylan, Tansu; Gan, Tianjun; Günther, Maximilian N.; Hellier, Coel; Horne, Keith; Huang, Chelsea X.; Jensen, Eric L. N.; Kielkopf, John; Palle, Enric; Sefako, Ramotholo; Stassun, Keivan G.; Tan, Thiam-Guan; Vanderburg, Andrew; Ricker, George R.; Latham, David W.; Vanderspek, Roland; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Colon, Knicole; Dressing, Courtney D.; Léepine, Sébastien; Muirhead, Philip S.; Rose, Mark E.; Twicken, Joseph D.; Villasenor, Jesus Noel
Abstract: We report the discovery of GJ 1252 b, a planet with a radius of 1.193 ± 0.074 ${R}_{\oplus }$ and an orbital period of 0.52 days around an M3-type star (0.381 ± 0.019 ${M}_{\odot }$ , 0.391 ± 0.020 ${R}_{\odot }$ ) located 20.385 ± 0.019 pc away. We use Transiting Exoplanet Survey Satellite (TESS) data, ground-based photometry and spectroscopy, Gaia astrometry, and high angular resolution imaging to show that the transit signal seen in the TESS data must originate from a transiting planet. We do so by ruling out all false-positive scenarios that attempt to explain the transit signal as originating from an eclipsing stellar binary. Precise Doppler monitoring also leads to a tentative mass measurement of 2.09 ± 0.56 M_⊕. The host star proximity, brightness (V = 12.19 mag, K = 7.92 mag), low stellar activity, and the system's short orbital period make this planet an attractive target for detailed characterization, including precise mass measurement, looking for other objects in the system, and planet atmosphere characterization.

ID: 155696
Type: article
Authors: Thao, Pa Chia; Mann, Andrew W.; Johnson, Marshall C.; Newton, Elisabeth R.; Guo, Xueying; Kain, Isabel J.; Rizzuto, Aaron C.; Charbonneau, David; Dalba, Paul A.; Gaidos, Eric; Irwin, Jonathan M.; Kraus, Adam L.
Abstract: Transiting planets in nearby young clusters offer the opportunity to study the atmospheres and dynamics of planets during their formative years. To this end, we focused on K2-25b-a close-in (P = 3.48 days), Neptune-sized exoplanet orbiting a M4.5 dwarf in the 650 Myr Hyades cluster. We combined photometric observations of K2-25 covering a total of 44 transits and spanning >2 yr, drawn from a mix of space-based telescopes (Spitzer Space Telescope and K2) and ground-based facilities (Las Cumbres Observatory Global Telescope network and MEarth). The transit photometry spanned 0.6─4.5 μm, which enabled our study of K2-25b's transmission spectrum. We combined and fit each data set at a common wavelength within a Markov Chain Monte Carlo framework, yielding consistent planet parameters. The resulting transit depths ruled out a solar-composition atmosphere for K2-25b for the range of expected planetary masses and equilibrium temperature at a >4σ confidence level, and are consistent with a flat transmission spectrum. Mass constraints and transit observations at a finer grid of wavelengths (e.g., from the Hubble Space Telescope) are needed to make more definitive statements about the presence of clouds or an atmosphere of high mean molecular weight. Our precise measurements of K2-25b's transit duration also enabled new constraints on the eccentricity of K2-25's orbit. We find K2-25b's orbit to be eccentric (e > 0.20) for all reasonable stellar densities and independent of the observation wavelength or instrument. The high eccentricity is suggestive of a complex dynamical history and motivates future searches for additional planets or stellar companions.

ID: 156878
Type: article
Authors: Winters, Jennifer G.; Irwin, Jonathan M.; Charbonneau, David; Latham, David W.; Medina, Amber M.; Mink, Jessica; Esquerdo, Gilbert A.; Berlind, Perry; Calkins, Michael L.; Berta-Thompson, Zachory K.
Abstract: We present the spectroscopic orbits of 11 nearby, mid-to-late M dwarf binary systems in a variety of configurations: 2 single-lined binaries (SB1s), 7 double-lined binaries (SB2s), 1 double-lined triple (ST2), and 1 triple-lined triple (ST3). Eight of these orbits are the first published for these systems, while five are newly identified multiples. We obtained multi-epoch, high-resolution spectra with the TRES instrument on the 1.5 m Tillinghast Reflector at the Fred Lawrence Whipple Observatory located on Mt. Hopkins in AZ. Using the TiO molecular bands at 7065-7165 Å, we calculated radial velocities for these systems, from which we derived their orbits. We find LHS 1817 to have in a 7 hr period a companion that is likely a white dwarf, due to the ellipsoidal modulation we see in our MEarth-North light-curve data. We find G 123-45 and LTT 11586 to host companions with minimum masses of 41 M_Jup and 44 M_Jup with orbital periods of 35 and 15 days, respectively. We find 2MA 0930+0227 to have a rapidly rotating stellar companion in a 917 day orbital period. GJ 268, GJ 1029, LP 734-34, GJ 1182, G 258-17, and LTT 7077are SB2s with stellar companions with orbital periods of 10, 96, 34, 154, 5, and 84 days; LP 655-43 is an ST3 with one companion in an 18 day orbital period and an outer component in a longer undetermined period. In addition, we present radial velocities for both components of L 870-44AB and for the outer components of LTT 11586 and LP 655-43.

ID: 154442
Type: article
Authors: Crossfield, Ian J. M.; Waalkes, William; Newton, Elisabeth R.; Narita, Norio; Muirhead, Philip; Ment, Kristo; Matthews, Elisabeth; Kraus, Adam; Kostov, Veselin; Kosiarek, Molly R.; Kane, Stephen R.; Isaacson, Howard; Halverson, Sam; Gonzales, Erica; Everett, Mark; Dragomir, Diana; Collins, Karen A.; Chontos, Ashley; Berardo, David; Winters, Jennifer G.; Winn, Joshua N.; Scott, Nicholas J.; Rojas-Ayala, Barbara; Rizzuto, Aaron C.; Petigura, Erik A.; Peterson, Merrin; Mocnik, Teo; Mikal-Evans, Thomas; Mehrle, Nicholas; Matson, Rachel; Kuzuhara, Masayuki; Irwin, Jonathan; Huber, Daniel; Huang, Chelsea; Howell, Steve; Howard, Andrew W.; Hirano, Teruyuki; Fulton, Benjamin J.; Dupuy, Trent; Dressing, Courtney D.; Dalba, Paul A.; Charbonneau, David; Burt, Jennifer; Berta-Thompson, Zachory; Benneke, Björn; Watanabe, Noriharu; Twicken, Joseph D.; Tamura, Motohide; Schlieder, Joshua; Seager, S.; Rose, Mark E.; Ricker, George; Quintana, Elisa; Lépine, Sébastien; Latham, David W.; Kotani, Takayuki; Jenkins, Jon M.; Hori, Yasunori; Colon, Knicole; Caldwell, Douglas A.
Abstract: Planets occur most frequently around cool dwarfs, but only a handful of specific examples are known to orbit the latest-type M stars. Using TESS photometry, we report the discovery of two planets transiting the low- mass star called LP 791-18 (identified by TESS as TOI 736). This star has spectral type M6V, effective temperature 2960 K, and radius 0.17 R _☉, making it the third-coolest star known to host planets. The two planets straddle the radius gap seen for smaller exoplanets they include a 1.1R _⊕ planet on a 0.95 day orbit and a 2.3R _⊕ planet on a 5 day orbit. Because the host star is small the decrease in light during these planets' transits is fairly large (0.4% and 1.7%). This has allowed us to detect both planets' transits from ground-based photometry, refining their radii and orbital ephemerides. In the future, radial velocity observations and transmission spectroscopy can both probe these planets' bulk interior and atmospheric compositions, and additional photometric monitoring would be sensitive to even smaller transiting planets.

ID: 154184
Type: article
Authors: Kostov, Veselin B.; Schlieder, Joshua E.; Barclay, Thomas; Quintana, Elisa V.; Colón, Knicole D.; Brande, Jonathan; Collins, Karen A.; Feinstein, Adina D.; Hadden, Samuel; Kane, Stephen R.; Kreidberg, Laura; Kruse, Ethan; Lam, Christopher; Matthews, Elisabeth; Montet, Benjamin T.; Pozuelos, Francisco J.; Stassun, Keivan G.; Winters, Jennifer G.; Ricker, George; Vanderspek, Roland; Latham, David; Seager, Sara; Winn, Joshua; Jenkins, Jon M.; Afanasev, Dennis; Armstrong, James J. D.; Arney, Giada; Boyd, Patricia; Barentsen, Geert; Barkaoui, Khalid; Batalha, Natalie E.; Beichman, Charles; Bayliss, Daniel; Burke, Christopher; Burdanov, Artem; Cacciapuoti, Luca; Carson, Andrew; Charbonneau, David; Christiansen, Jessie; Ciardi, David; Clampin, Mark; Collins, Kevin I.; Conti, Dennis M.; Coughlin, Jeffrey; Covone, Giovanni; Crossfield, Ian; Delrez, Laetitia; Domagal-Goldman, Shawn; Dressing, Courtney; Ducrot, Elsa; Essack, Zahra; Everett, Mark E.; Fauchez, Thomas; Foreman-Mackey, Daniel; Gan, Tianjun; Gilbert, Emily; Gillon, Michaël; Gonzales, Erica; Hamann, Aaron; Hedges, Christina; Hocutt, Hannah; Hoffman, Kelsey; Horch, Elliott P.; Horne, Keith; Howell, Steve; Hynes, Shane; Ireland, Michael; Irwin, Jonathan M.; Isopi, Giovanni; Jensen, Eric L. N.; Jehin, Emmanuël; Kaltenegger, Lisa; Kielkopf, John F.; Kopparapu, Ravi; Lewis, Nikole; Lopez, Eric; Lissauer, Jack J.; Mann, Andrew W.; Mallia, Franco; Mandell, Avi; Matson, Rachel A.; Mazeh, Tsevi; Monsue, Teresa; Moran, Sarah E.; Moran, Vickie; Morley, Caroline V.; Morris, Brett; Muirhead, Philip; Mukai, Koji; Mullally, Susan; Mullally, Fergal; Murray, Catriona; Narita, Norio; Palle, Enric; Pidhorodetska, Daria; Quinn, David; Relles, Howard; Rinehart, Stephen; Ritsko, Matthew; Rodriguez, Joseph E.; Rowden, Pamela; Rowe, Jason F.; Sebastian, Daniel; Sefako, Ramotholo; Shahaf, Sahar; Shporer, Avi; Tañón Reyes, Naylynn; Tenenbaum, Peter; Ting, Eric B.; Twicken, Joseph D.; van Belle, Gerard T.; Vega, Laura; Volosin, Jeffrey; Walkowicz, Lucianne M.; Youngblood, Allison
Abstract: We report the Transiting Exoplanet Survey Satellite (TESS) discovery of three terrestrial-size planets transiting L 98-59 (TOI-175, TIC 307210830)-a bright M dwarf at a distance of 10.6 pc. Using the Gaia- measured distance and broadband photometry, we find that the host star is an M3 dwarf. Combined with the TESS transits from three sectors, the corresponding stellar parameters yield planet radii ranging from 0.8 R _⊕ to 1.6 R _⊕. All three planets have short orbital periods, ranging from 2.25 to 7.45 days with the outer pair just wide of a 2:1 period resonance. Diagnostic tests produced by the TESS Data Validation Report and the vetting package DAVE rule out common false- positive sources. These analyses, along with dedicated follow-up and the multiplicity of the system, lend confidence that the observed signals are caused by planets transiting L 98-59 and are not associated with other sources in the field. The L 98-59 system is interesting for a number of reasons: the host star is bright (V = 11.7 mag, K = 7.1 mag) and the planets are prime targets for further follow-up observations including precision radial-velocity mass measurements and future transit spectroscopy with the James Webb Space Telescope; the near-resonant configuration makes the system a laboratory to study planetary system dynamical evolution; and three planets of relatively similar size in the same system present an opportunity to study terrestrial planets where other variables (age, metallicity, etc.) can be held constant. L 98-59 will be observed in four more TESS sectors, which will provide a wealth of information on the three currently known planets and have the potential to reveal additional planets in the system.

ID: 150413
Type: article
Authors: Ment, Kristo; Dittmann, Jason A.; Astudillo-Defru, Nicola; Charbonneau, David; Irwin, Jonathan; Bonfils, Xavier; Murgas, Felipe; Almenara, Jose-Manuel; Forveille, Thierry; Agol, Eric; Ballard, Sarah; Berta-Thompson, Zachory K.; Bouchy, François; Cloutier, Ryan; Delfosse, Xavier; Doyon, René; Dressing, Courtney D.; Esquerdo, Gilbert A.; Haywood, Raphaëlle D.; Kipping, David M.; Latham, David W.; Lovis, Christophe; Newton, Elisabeth R.; Pepe, Francesco; Rodriguez, Joseph E.; Santos, Nuno C.; Tan, Thiam-Guan; Udry, Stephane; Winters, Jennifer G.; Wünsche, Anaël
Abstract: LHS 1140 is a nearby mid-M dwarf known to host a temperate rocky super-Earth (LHS 1140 b) on a 24.737-day orbit. Based on photometric observations by MEarth and Spitzer as well as Doppler spectroscopy from the High Accuracy Radial velocity Planet Searcher, we report the discovery of an additional transiting rocky companion (LHS 1140 c) with a mass of 1.81 ± 0.39 M _⊕ and a radius of 1.282 ± 0.024 R _⊕ on a tighter, 3.77795-day orbit. We also obtain more precise estimates for the mass and radius of LHS 1140 b, which are 6.98 ± 0.89 M _⊕ and 1.727 ± 0.032 R _⊕. The mean densities of planets b and c are 7.5 ± 1.0 g cm^‑3 and 4.7 ± 1.1 g cm^‑3, respectively, both consistent with the Earth’s ratio of iron to magnesium silicate. The orbital eccentricities of LHS 1140 b and c are consistent with circular orbits and constrained to be below 0.06 and 0.31, respectively, with 90% confidence. Because the orbits of the two planets are coplanar and because we know from previous analyses of Kepler data that compact systems of small planets orbiting M dwarfs are commonplace, a search for more transiting planets in the LHS 1140 system could be fruitful. LHS 1140 c is one of the few known nearby terrestrial planets whose atmosphere could be studied with the upcoming James Webb Space Telescope.

ID: 150418
Type: article
Authors: Mondrik, Nicholas; Newton, Elisabeth; Charbonneau, David; Irwin, Jonathan
Abstract: We present an analysis of flares in mid-to-late M dwarfs in the MEarth photometric survey. We search 3,985,155 observations across 2226 stars, and detect 54 large (Δm ≥ 0.018) flares in total, distributed across 34 stars. We combine our flare measurements with recent activity and rotation period results from MEarth to show that there is an increase in flares per observation from low Rossby number (R _{o o o} > 0.44, slow rotators) to the intermediate population at the 99.97% level. We posit that the rise in flare rate for intermediate R _o could be due to changing magnetic field geometry on the surface of the star.

ID: 150534
Type: article
Authors: Vanderspek, Roland; Huang, Chelsea X.; Vanderburg, Andrew; Ricker, George R.; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Burt, Jennifer; Dittmann, Jason; Newton, Elisabeth; Quinn, Samuel N.; Shporer, Avi; Charbonneau, David; Irwin, Jonathan; Ment, Kristo; Winters, Jennifer G.; Collins, Karen A.; Evans, Phil; Gan, Tianjun; Hart, Rhodes; Jensen, Eric L. N.; Kielkopf, John; Mao, Shude; Waalkes, William; Bouchy, François; Marmier, Maxime; Nielsen, Louise D.; Ottoni, Gaël; Pepe, Francesco; Ségransan, Damien; Udry, Stéphane; Henry, Todd; Paredes, Leonardo A.; James, Hodari-Sadiki; Hinojosa, Rodrigo H.; Silverstein, Michele L.; Palle, Enric; Berta-Thompson, Zachory; Crossfield, Ian; Davies, Misty D.; Dragomir, Diana; Fausnaugh, Michael; Glidden, Ana; Pepper, Joshua; Morgan, Edward H.; Rose, Mark; Twicken, Joseph D.; Villaseñor, Jesus Noel S.; Yu, Liang; Bakos, Gaspar; Bean, Jacob; Buchhave, Lars A.; Christensen-Dalsgaard, Jørgen; Christiansen, Jessie L.; Ciardi, David R.; Clampin, Mark; De Lee, Nathan; Deming, Drake; Doty, John; Jernigan, J. Garrett; Kaltenegger, Lisa; Lissauer, Jack J.; McCullough, P. R.; Narita, Norio; Paegert, Martin; Pal, Andras; Rinehart, Stephen; Sasselov, Dimitar; Sato, Bun'ei; Sozzetti, Alessandro; Stassun, Keivan G.; Torres, Guillermo
Abstract: Data from the newly commissioned Transiting Exoplanet Survey Satellite has revealed a "hot Earth" around LHS 3844, an M dwarf located 15 pc away. The planet has a radius of 1.303+/- 0.022 R _⊕ and orbits the star every 11 hr. Although the existence of an atmosphere around such a strongly irradiated planet is questionable, the star is bright enough (I = 11.9, K = 9.1) for this possibility to be investigated with transit and occultation spectroscopy. The star's brightness and the planet's short period will also facilitate the measurement of the planet's mass through Doppler spectroscopy.

ID: 155127
Type: article
Authors: Waalkes, William C.; Berta-Thompson, Zachory; Bourrier, Vincent; Newton, Elisabeth; Ehrenreich, David; Kempton, Eliza M. -R; Charbonneau, David; Irwin, Jonathan; Dittmann, Jason
Abstract: GJ 1132b, which orbits an M dwarf, is one of the few known Earth-sized planets, and at 12 pc away it is one of the closest known transiting planets. Receiving roughly 19× Earth's insolation, this planet is too hot to be habitable but can inform us about the volatile content of rocky planet atmospheres around cool stars. Using Hubble Space Telescope Imaging Spectrograph spectra, we search for a transit in the Lyα line of neutral hydrogen (Lyα). If we were to observe a deep Lyα absorption signature, that would indicate the presence of a neutral hydrogen envelope flowing from GJ 1132b. On the other hand, ruling out deep absorption from neutral hydrogen may indicate that this planet does not have a detectable amount of hydrogen loss, is not losing hydrogen, or has lost hydrogen and other volatiles early in the star's life. We do not detect a transit and determine a 2σ upper limit on the effective envelope radius of 0.36 R _* in the red wing of the Lyα line, which is the only portion of the spectrum we detect after absorption by the ISM. We analyze the Lyα spectrum and stellar variability of GJ1132, which is a slowly rotating 0.18 solar mass M dwarf with previously uncharacterized UV activity. Our data show stellar variabilities of 5%-22%, which is consistent with the M dwarf UV variabilities of up to 41% found by Loyd & France. Understanding the role that UV variability plays in planetary atmospheres is crucial to assess atmospheric evolution and the habitability of cooler rocky exoplanets.

ID: 154724
Type: article
Authors: Winters, Jennifer G.; Medina, Amber A.; Irwin, Jonathan M.; Charbonneau, David; Astudillo-Defru, Nicola; Horch, Elliott P.; Eastman, Jason D.; Halley Vrijmoet, Eliot; Henry, Todd J.; Diamond-Lowe, Hannah; Winston, Elaine; Barclay, Thomas; Bonfils, Xavier; Ricker, George R.; Vanderspek, Roland; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Udry, Stéphane; Twicken, Joseph D.; Teske, Johanna K.; Tenenbaum, Peter; Pepe, Francesco; Murgas, Felipe; Muirhead, Philip S.; Mink, Jessica; Lovis, Christophe; Levine, Alan M.; Lépine, Sébastien; Jao, Wei-Chun; Henze, Christopher E.; Furész, Gábor; Forveille, Thierry; Figueira, Pedro; Esquerdo, Gilbert A.; Dressing, Courtney D.; Díaz, Rodrigo F.; Delfosse, Xavier; Burke, Christopher J.; Bouchy, François; Berlind, Perry; Almenara, Jose-Manuel
Abstract: We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of 6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing Operations Center data validation report to determine that the planet transits the primary star in the system. The planet has a radius of {1.38}_-0.12^+0.13 {R}_\oplus , an orbital period of {5.35882}_-0.00031^+0.00030 days, and an equilibrium temperature of {433}_-27⁺²⁸ K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper mass limit of 8.4 {M}_\oplus on the planet. LTT 1445Ab provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system hints that the entire system may be co- planar, implying that the system may have formed from the early fragmentation of an individual protostellar core.

ID: 149410
Type: article
Authors: Bonfils, X.; Almenara, J. -M; Cloutier, R.; Wünsche, A.; Astudillo-Defru, N.; Berta-Thompson, Z.; Bouchy, F.; Charbonneau, David; Delfosse, X.; Díaz, R. F.; Dittmann, J.; Doyon, R.; Forveille, T.; Irwin, Jonathan M.; Lovis, C.; Mayor, M.; Menou, K.; Murgas, F.; Newton, E.; Pepe, F.; Santos, N. C.; Udry, S.
Abstract: The source GJ1132 is a nearby red dwarf known to host a transiting Earth-size planet. After its initial detection, we pursued an intense follow-up with the HARPS velocimeter. We now confirm the detection of GJ1132b with radial velocities alone. We refined its orbital parameters, and in particular, its mass (m_b = 1.66 ± 0.23 M_⊕), density (ρ_b = 6.3 ± 1.3 g cm^-3), and eccentricity (e_{b c} = 8.93 ± 0.01 days and minimum mass m_c sini_c = 2.64 ± 0.44 M_⊕. Receiving about 1.9 times more flux than Earth in our solar system, its equilibrium temperature is that of a temperate planet (T_eq = 230-300 K for albedos A = 0.75 - 0.00), which places GJ1132c near the inner edge of the so-called habitable zone. Despite an a priori favorable orientation for the system, Spitzer observations reject most transit configurations, leaving a posterior probability = 230-300 K for albedos A = 0.75 - 0.00), which places GJ1132c near the inner edge of the so-called habitable zone. Despite an a priori favorable orientation for the system, Spitzer observations reject most transit configurations, leaving a posterior probability _d = 177 ± 5 days attributed to either a planet candidate with minimum mass m_d sin i_d = 8.4_-2.5^+1.7 M_⊕ or stellar activity. Its Doppler signal is the most powerful in our HARPS time series but appears on a timescale where either the stellar rotation or a magnetic cycle are viable alternatives to the planet hypothesis. On the one hand, the period is different than that measured for the stellar rotation ( 125 days), and a Bayesian statistical analysis we performed with a Markov chain Monte Carlo and Gaussian processes demonstrates that the signal is better described by a Keplerian function than by correlated noise. On the other hand, periodograms of spectral indices sensitive to stellar activity show power excess at similar periods to that of this third signal, and radial velocity shifts induced by stellar activity can also match a Keplerian function. We, therefore, prefer to leave the status of GJ1132(d) undecided. Based on observations made with the HARPS instrument on the ESO 3.6 m telescope under the program IDs 191.C-0873(A), and 198.C-0838(A), at Cerro La Silla (Chile).Radial velocity data 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/qcat?J/A+A/618/A142