Publication Search Results

ID: 158590
Type: article
Authors: Hosseinzadeh, Griffin; Dauphin, Frederick; Villar, Victoria Ashley; Berger, Edo; Jones, David O.; Challis, Peter; Chornock, Ryan; Drout, Maria R.; Foley, Ryan J.; Kirshner, Robert P.; Lunnan, Ragnhild; Margutti, Raffaella; Milisavljevic, Dan; Pan, Yen-Chen; Rest, Armin; Scolnic, Daniel M.; Magnier, Eugene; Metcalfe, Nigel; Wainscoat, Richard; Waters, Christopher
Abstract: The classification of supernovae (SNe) and its impact on our understanding of explosion physics and progenitors have traditionally been based on the presence or absence of certain spectral features. However, current and upcoming wide-field time-domain surveys have increased the transient discovery rate far beyond our capacity to obtain even a single spectrum of each new event. We must therefore rely heavily on photometric classification-connecting SN light curves back to their spectroscopically defined classes. Here, we present Superphot, an open-source Python implementation of the machine-learning classification algorithm of Villar et al., and apply it to 2315 previously unclassified transients from the Pan-STARRS1 Medium Deep Survey for which we obtained spectroscopic host-galaxy redshifts. Our classifier achieves an overall accuracy of 82%, with completenesses and purities of >80% for the best classes (SNe Ia and superluminous SNe). For the worst performing SN class (SNe Ibc), the completeness and purity fall to 37% and 21%, respectively. Our classifier provides 1257 newly classified SNe Ia, 521 SNe II, 298 SNe Ibc, 181 SNe IIn, and 58 SLSNe. These are among the largest uniformly observed samples of SNe available in the literature and will enable a wide range of statistical studies of each class.

ID: 158589
Type: article
Authors: Villar, Victoria Ashley; Hosseinzadeh, Griffin; Berger, Edo; Ntampaka, Michelle; Jones, David O.; Challis, Peter; Chornock, Ryan; Drout, Maria R.; Foley, Ryan J.; Kirshner, Robert P.; Lunnan, Ragnhild; Margutti, Raffaella; Milisavljevic, Dan; Sanders, Nathan; Pan, Yen-Chen; Rest, Armin; Scolnic, Daniel M.; Magnier, Eugene; Metcalfe, Nigel; Wainscoat, Richard; Waters, Christopher
Abstract: Automated classification of supernovae (SNe) based on optical photometric light-curve information is essential in the upcoming era of wide-field time domain surveys, such as the Legacy Survey of Space and Time (LSST) conducted by the Rubin Observatory. Photometric classification can enable real-time identification of interesting events for extended multiwavelength follow-up, as well as archival population studies. Here we present the complete sample of 5243 "SN-like" light curves (in g_P1r_P1i_P1z_P1) from the Pan-STARRS1 Medium-Deep Survey (PS1-MDS). The PS1-MDS is similar to the planned LSST Wide-Fast-Deep survey in terms of cadence, filters, and depth, making this a useful training set for the community. Using this data set, we train a novel semisupervised machine learning algorithm to photometrically classify 2315 new SN-like light curves with host galaxy spectroscopic redshifts. Our algorithm consists of an RF supervised classification step and a novel unsupervised step in which we introduce a recurrent autoencoder neural network (RAENN). Our final pipeline, dubbed SuperRAENN, has an accuracy of 87% across five SN classes (Type Ia, Ibc, II, IIn, SLSN-I) and macro-averaged purity and completeness of 66% and 69%, respectively. We find the highest accuracy rates for SNe Ia and SLSNe and the lowest for SNe Ibc. Our complete spectroscopically and photometrically classified samples break down into 62.0% Type Ia (1839 objects), 19.8% Type II (553 objects), 4.8% Type IIn (136 objects), 11.7% Type Ibc (291 objects), and 1.6% Type I SLSNe (54 objects).

ID: 150428
Type: article
Authors: Dimitriadis, G.; Foley, R. J.; Rest, A.; Kasen, D.; Piro, A. L.; Polin, A.; Jones, D. O.; Villar, Victoria Ashley; Narayan, G.; Coulter, D. A.; Kilpatrick, C. D.; Pan, Y. -C; Rojas-Bravo, C.; Fox, O. D.; Jha, S. W.; Nugent, P. E.; Riess, A. G.; Scolnic, D.; Drout, M. R.; K2 Mission Team; Barentsen, G.; Dotson, J.; Gully-Santiago, M.; Hedges, C.; Cody, A. M.; Barclay, T.; Howell, S.; KEGS; Garnavich, P.; Tucker, B. E.; Shaya, E.; Mushotzky, R.; Olling, R. P.; Margheim, S.; Zenteno, A.; Kepler spacecraft team; Coughlin, J.; Van Cleve, Jeffrey E.; Cardoso, J. Vinícius de Miranda; Larson, K. A.; McCalmont-Everton, K. M.; Peterson, C. A.; Ross, S. E.; Reedy, L. H.; Osborne, D.; Mcginn, C.; Kohnert, L.; Migliorini, L.; Wheaton, A.; Spencer, B.; Labonde, C.; Castillo, G.; Beerman, G.; Steward, K.; Hanley, M.; Larsen, R.; Gangopadhyay, R.; Kloetzel, R.; Weschler, T.; Nystrom, V.; Moffatt, J.; Redick, M.; Griest, K.; Packard, M.; Muszynski, M.; Kampmeier, J.; Bjella, R.; Flynn, S.; Elsaesser, B.; Pan-STARRS; Chambers, K. C.; Flewelling, H. A.; Huber, M. E.; Magnier, E. A.; Waters, C. Z.; Schultz, A. S. B.; Bulger, J.; Lowe, T. B.; Willman, M.; Smartt, S. J.; Smith, K. W.; DECam; Points, S.; Strampelli, G. M.; ASAS-SN; Brimacombe, J.; Chen, P.; Muñoz, J. A.; Mutel, R. L.; Shields, J.; Vallely, P. J.; Villanueva, S., Jr.; PTSS/TNTS; Li, W.; Wang, X.; Zhang, J.; Lin, H.; Mo, J.; Zhao, X.; Sai, H.; Zhang, X.; Zhang, K.; Zhang, T.; Wang, L.; Zhang, J.; Baron, E.; DerKacy, J. M.; Li, L.; Chen, Z.; Xiang, D.; Rui, L.; Wang, L.; Huang, F.; Li, X.; Cumbres Observatory, Las; Hosseinzadeh, G.; Howell, D. A.; Arcavi, I.; Hiramatsu, D.; Burke, J.; Valenti, S.; ATLAS; Tonry, J. L.; Denneau, L.; Heinze, A. N.; Weiland, H.; Stalder, B.; Konkoly; Vinkó, J.; Sárneczky, K.; Pál, A.; Bódi, A.; Bognár, Zs; Csák, B.; Cseh, B.; Csörnyei, G.; Hanyecz, O.; Ignácz, B.; Kalup, Cs; Könyves-Tóth, R.; Kriskovics, L.; Ordasi, A.; Rajmon, I.; Sódor, A.; Szabó, R.; Szakáts, R.; Zsidi, G.; ePESSTO; Williams, S. C.; Nordin, J.; Cartier, R.; Frohmaier, C.; Galbany, L.; Gutiérrez, C. P.; Hook, I.; Inserra, C.; Smith, M.; Arizona, University of; Sand, D. J.; Andrews, J. E.; Smith, N.; Bilinski, C.
Abstract: We present an exquisite 30 minute cadence Kepler (K2) light curve of the Type Ia supernova (SN Ia) 2018oh (ASASSN-18bt), starting weeks before explosion, covering the moment of explosion and the subsequent rise, and continuing past peak brightness. These data are supplemented by multi-color Panoramic Survey Telescope (Pan-STARRS1) and Rapid Response System 1 and Cerro Tololo Inter-American Observatory 4 m Dark Energy Camera (CTIO 4-m DECam) observations obtained within hours of explosion. The K2 light curve has an unusual two-component shape, where the flux rises with a steep linear gradient for the first few days, followed by a quadratic rise as seen for typical supernovae (SNe) Ia. This “flux excess” relative to canonical SN Ia behavior is confirmed in our i-band light curve, and furthermore, SN 2018oh is especially blue during the early epochs. The flux excess peaks 2.14 ± 0.04 days after explosion, has a FWHM of 3.12 ± 0.04 days, a blackbody temperature of T=17,{500}_-9,000^+11,500 K, a peak luminosity of 4.3+/- 0.2× {10}³⁷ {erg} {{{s}}}^-1, and a total integrated energy of 1.27+/- 0.01× {10}⁴³ {erg}. We compare SN 2018oh to several models that may provide additional heating at early times, including collision with a companion and a shallow concentration of radioactive nickel. While all of these models generally reproduce the early K2 light curve shape, we slightly favor a companion interaction, at a distance of ∼2× {10}¹² {cm} based on our early color measurements, although the exact distance depends on the uncertain viewing angle. Additional confirmation of a companion interaction in future modeling and observations of SN 2018oh would provide strong support for a single-degenerate progenitor system.

ID: 155119
Type: article
Authors: Hosseinzadeh, Griffin; Cowperthwaite, P. S.; Gomez, Sebastian; Villar, Victoria Ashley; Nicholl, M.; Margutti, R.; Berger, Edo; Chornock, R.; Paterson, K.; Fong, W.; Savchenko, V.; Short, P.; Alexander, K. D.; Blanchard, Peter K.; Braga, J.; Calkins, Michael L.; Cartier, R.; Coppejans, D. L.; Eftekhari, Tarraneh; Laskar, T.; Ly, C.; Patton, Locke; Pelisoli, I.; Reichart, D. E.; Terreran, G.; Williams, Peter K. G.
Abstract: On 2019 April 25.346 and 26.640 UT the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo gravitational-wave (GW) observatory announced the detection of the first candidate events in Observing Run 3 that contained at least one neutron star (NS). S190425z is a likely binary neutron star (BNS) merger at d _L = 156 ± 41 Mpc, while S190426c is possibly the first NS-black hole (BH) merger ever detected, at d _L = 377 ± 100 Mpc, although with marginal statistical significance. Here we report our optical follow-up observations for both events using the MMT 6.5 m telescope, as well as our spectroscopic follow-up of candidate counterparts (which turned out to be unrelated) with the 4.1 m SOAR telescope. We compare to publicly reported searches, explore the overall areal coverage and depth, and evaluate those in relation to the optical/near-infrared (NIR) kilonova emission from the BNS merger GW170817, to theoretical kilonova models, and to short gamma-ray burst (SGRB) afterglows. We find that for a GW170817-like kilonova, the partial volume covered spans up to about 40% for S190425z and 60% for S190426c. For an on-axis jet typical of SGRBs, the search effective volume is larger, but such a configuration is expected in at most a few percent of mergers. We further find that wide- field γ-ray and X-ray limits rule out luminous on-axis SGRBs, for a large fraction of the localization regions, although these searches are not sufficiently deep in the context of the γ-ray emission from GW170817 or off-axis SGRB afterglows. The results indicate that some optical follow-up searches are sufficiently deep for counterpart identification to about 300 Mpc, but that localizations better than 1000 deg² are likely essential.

ID: 154436
Type: article
Authors: Kessler, R.; Narayan, G.; Avelino, Arturo; Bachelet, E.; Biswas, R.; Brown, P. J.; Chernoff, D. F.; Connolly, A. J.; Dai, M.; Daniel, S.; Di Stefano, Rosanne; Drout, M. R.; Galbany, L.; González-Gaitán, S.; Graham, M. L.; Hložek, R.; Ishida, E. E. O.; Guillochon, James; Jha, S. W.; Jones, D. O.; Mandel, K. S.; Muthukrishna, D.; O'Grady, A.; Peters, C. M.; Pierel, J. R.; Ponder, K. A.; Prša, A.; Rodney, S.; Villar, Victoria Ashley; LSST Dark Energy Science Collaboration; Transient and Variable Stars Science Collaboration
Abstract: We describe the simulated data sample for the Photometric Large Synoptic Survey Telescope (LSST) Astronomical Time Series Classification Challenge (PLAsTiCC), a publicly available challenge to classify transient and variable events that will be observed by the LSST, a new facility expected to start in the early 2020s. The challenge was hosted by Kaggle, ran from 2018 September 28 to December 17, and included 1094 teams competing for prizes. Here we provide details of the 18 transient and variable source models, which were not revealed until after the challenge, and release the model libraries at https://doi.org/10.5281/zenodo.2612896. We describe the LSST Operations Simulator used to predict realistic observing conditions, and we describe the publicly available SNANA simulation code used to transform the models into observed fluxes and uncertainties in the LSST passbands (ugrizy). Although PLAsTiCC has finished, the publicly available models and simulation tools are being used within the astronomy community to further improve classification, and to study contamination in photometrically identified samples of SN Ia used to measure properties of dark energy. Our simulation framework will continue serving as a platform to improve the PLAsTiCC models, and to develop new models.

ID: 150419
Type: article
Authors: Li, W.; Wang, X.; Vinkó, J.; Mo, J.; Hosseinzadeh, Griffin; Sand, D. J.; Zhang, J.; Lin, H.; PTSS/TNTS; Zhang, T.; Wang, L.; Zhang, J.; Chen, Z.; Xiang, D.; Rui, L.; Huang, F.; Li, X.; Zhang, X.; Li, L.; Baron, E.; DerKacy, J. M.; Zhao, X.; Sai, H.; Zhang, K.; Wang, L.; LCO; Howell, D. A.; McCully, C.; Arcavi, I.; Valenti, S.; Hiramatsu, D.; Burke, J.; KEGS; Rest, A.; Garnavich, P.; Tucker, B. E.; Narayan, G.; Shaya, E.; Margheim, S.; Zenteno, A.; Villar, Victoria Ashley; UCSC; Dimitriadis, G.; Foley, R. J.; Pan, Y. -C; Coulter, D. A.; Fox, O. D.; Jha, S. W.; Jones, D. O.; Kasen, D. N.; Kilpatrick, C. D.; Piro, A. L.; Riess, A. G.; Rojas-Bravo, C.; ASAS-SN; Shappee, B. J.; Holoien, T. W. -S; Stanek, K. Z.; Drout, M. R.; Auchettl, K.; Kochanek, C. S.; Brown, J. S.; Bose, S.; Bersier, D.; Brimacombe, J.; Chen, P.; Dong, S.; Holmbo, S.; Muñoz, J. A.; Mutel, R. L.; Post, R. S.; Prieto, J. L.; Shields, J.; Tallon, D.; Thompson, T. A.; Vallely, P. J.; Villanueva, S., Jr.; Pan-STARRS; Smartt, S. J.; Smith, K. W.; Chambers, K. C.; Flewelling, H. A.; Huber, M. E.; Magnier, E. A.; Waters, C. Z.; Schultz, A. S. B.; Bulger, J.; Lowe, T. B.; Willman, M.; Konkoly/Texas; Sárneczky, K.; Pál, A.; Wheeler, J. C.; Bódi, A.; Bognár, Zs; Csák, B.; Cseh, B.; Csörnyei, G.; Hanyecz, O.; Ignácz, B.; Kalup, Cs; Könyves-Tóth, R.; Kriskovics, L.; Ordasi, A.; Rajmon, I.; Sódor, A.; Szabó, R.; Szakáts, R.; Zsidi, G.; Arizona, University of; Milne, P.; Andrews, J. E.; Smith, N.; Bilinski, C.; Swift; Brown, P. J.; ePESSTO; Nordin, J.; Williams, S. C.; Galbany, L.; Palmerio, J.; Hook, I. M.; Inserra, C.; Maguire, K.; Cartier, Régis; Razza, A.; Gutiérrez, C. P.; North Carolina, University of; Hermes, J. J.; Reding, J. S.; Kaiser, B. C.; ATLAS; Tonry, J. L.; Heinze, A. N.; Denneau, L.; Weiland, H.; Stalder, B.; K2 Mission Team; Barentsen, G.; Dotson, J.; Barclay, T.; Gully-Santiago, M.; Hedges, C.; Cody, A. M.; Howell, S.; Kepler spacecraft team; Coughlin, J.; Van Cleve, Jeffrey E.; Cardoso, J. Vinícius de Miranda; Larson, K. A.; McCalmont-Everton, K. M.; Peterson, C. A.; Ross, S. E.; Reedy, L. H.; Osborne, D.; Mcginn, C.; Kohnert, L.; Migliorini, L.; Wheaton, A.; Spencer, B.; Labonde, C.; Castillo, G.; Beerman, G.; Steward, K.; Hanley, M.; Larsen, R.; Gangopadhyay, R.; Kloetzel, R.; Weschler, T.; Nystrom, V.; Moffatt, J.; Redick, M.; Griest, K.; Packard, M.; Muszynski, M.; Kampmeier, J.; Bjella, R.; Flynn, S.; Elsaesser, B.
Abstract: Supernova (SN) 2018oh (ASASSN-18bt) is the first spectroscopically confirmed Type Ia supernova (SN Ia) observed in the Kepler field. The Kepler data revealed an excess emission in its early light curve, allowing us to place interesting constraints on its progenitor system. Here we present extensive optical, ultraviolet, and near-infrared photometry, as well as dense sampling of optical spectra, for this object. SN 2018oh is relatively normal in its photometric evolution, with a rise time of 18.3 ± 0.3 days and Δm ₁₅(B) = 0.96 ± 0.03 mag, but it seems to have bluer B ‑ V colors. We construct the “UVOIR” bolometric light curve having a peak luminosity of 1.49 × 10⁴³ erg s^‑1, from which we derive a nickel mass as 0.55 ± 0.04 M _⊙ by fitting radiation diffusion models powered by centrally located ⁵⁶Ni. Note that the moment when nickel-powered luminosity starts to emerge is +3.85 days after the first light in the Kepler data, suggesting other origins of the early-time emission, e.g., mixing of ⁵⁶Ni to outer layers of the ejecta or interaction between the ejecta and nearby circumstellar material or a nondegenerate companion star. The spectral evolution of SN 2018oh is similar to that of a normal SN Ia but is characterized by prominent and persistent carbon absorption features. The C II features can be detected from the early phases to about 3 weeks after the maximum light, representing the latest detection of carbon ever recorded in an SN Ia. This indicates that a considerable amount of unburned carbon exists in the ejecta of SN 2018oh and may mix into deeper layers.

ID: 150420
Type: article
Authors: Shappee, B. J.; Holoien, T. W. -S; Drout, M. R.; Auchettl, K.; Stritzinger, M. D.; Kochanek, C. S.; Stanek, K. Z.; Shaya, E.; Narayan, G.; ASAS-SN; Brown, J. S.; Bose, S.; Bersier, D.; Brimacombe, J.; Chen, Ping; Dong, Subo; Holmbo, S.; Katz, B.; Muñoz, J. A.; Mutel, R. L.; Post, R. S.; Prieto, J. L.; Shields, J.; Tallon, D.; Thompson, T. A.; Vallely, P. J.; Villanueva, S., Jr.; ATLAS; Denneau, L.; Flewelling, H.; Heinze, A. N.; Smith, K. W.; Stalder, B.; Tonry, J. L.; Weiland, H.; Kepler/K2; Barclay, T.; Barentsen, G.; Cody, A. M.; Dotson, J.; Foerster, F.; Garnavich, P.; Gully-Santiago, M.; Hedges, C.; Howell, S.; Kasen, D.; Margheim, S.; Mushotzky, R.; Rest, A.; Tucker, B. E.; Villar, Victoria Ashley; Zenteno, A.; Kepler spacecraft team; Beerman, G.; Bjella, R.; Castillo, G.; Coughlin, J.; Elsaesser, B.; Flynn, S.; Gangopadhyay, R.; Griest, K.; Hanley, M.; Kampmeier, J.; Kloetzel, R.; Kohnert, L.; Labonde, C.; Larsen, R.; Larson, K. A.; McCalmont-Everton, K. M.; Mcginn, C.; Migliorini, L.; Moffatt, J.; Muszynski, M.; Nystrom, V.; Osborne, D.; Packard, M.; Peterson, C. A.; Redick, M.; Reedy, L. H.; Ross, S. E.; Spencer, B.; Steward, K.; Van Cleve, Jeffrey E.; Cardoso, J. Vinícius de Miranda; Weschler, T.; Wheaton, A.; Pan-STARRS; Bulger, J.; Chambers, K. C.; Flewelling, H. A.; Huber, M. E.; Lowe, T. B.; Magnier, E. A.; Schultz, A. S. B.; Waters, C. Z.; Willman, M.; PTSS/TNTS; Baron, E.; Chen, Zhihao; Derkacy, James M.; Huang, Fang; Li, Linyi; Li, Wenxiong; Li, Xue; Mo, Jun; Rui, Liming; Sai, Hanna; Wang, Lifan; Wang, Lingzhi; Wang, Xiaofeng; Xiang, Danfeng; Zhang, Jicheng; Zhang, Jujia; Zhang, Kaicheng; Zhang, Tianmeng; Zhang, Xinghan; Zhao, Xulin; Brown, P. J.; Hermes, J. J.; Nordin, J.; Points, S.; Sódor, A.; Strampelli, G. M.; Zenteno, A.
Abstract: On 2018 February 4.41, the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered ASASSN-18bt in the K2 Campaign 16 field. With a 14.31, ASASSN-18bt is the nearest and brightest SNe Ia yet observed by the Kepler spacecraft. Here we present the discovery of ASASSN-18bt, the K2 light curve, and prediscovery data from ASAS-SN and the Asteroid Terrestrial-impact Last Alert System. The K2 early-time light curve has an unprecedented 30-minute cadence and photometric precision for an SN Ia light curve, and it unambiguously shows a ∼4 day nearly linear phase followed by a steeper rise. Thus, ASASSN-18bt joins a growing list of SNe Ia whose early light curves are not well described by a single power law. We show that a double-power-law model fits the data reasonably well, hinting that two physical processes must be responsible for the observed rise. However, we find that current models of the interaction with a nondegenerate companion predict an abrupt rise and cannot adequately explain the initial, slower linear phase. Instead, we find that existing published models with shallow ⁵⁶Ni are able to span the observed behavior and, with tuning, may be able to reproduce the ASASSN-18bt light curve. Regardless, more theoretical work is needed to satisfactorily model this and other early-time SNe Ia light curves. Finally, we use Swift X-ray nondetections to constrain the presence of circumstellar material (CSM) at much larger distances and lower densities than possible with the optical light curve. For a constant-density CSM, these nondetections constrain ρ Ni are able to span the observed behavior and, with tuning, may be able to reproduce the ASASSN-18bt light curve. Regardless, more theoretical work is needed to satisfactorily model this and other early-time SNe Ia light curves. Finally, we use Swift X-ray nondetections to constrain the presence of circumstellar material (CSM) at much larger distances and lower densities than possible with the optical light curve. For a constant-density CSM, these nondetections constrain ρ ⁵ cm^‑3 at a radius of 4 × 10¹⁵ cm from the progenitor star. Assuming a wind-like environment, we place mass loss limits of \dot{M} cm from the progenitor star. Assuming a wind-like environment, we place mass loss limits of \dot{M}^-6 {M}_ȯ {yr}}^-1 for v _w = 100 km s^‑1, ruling out some symbiotic progenitor systems. This work highlights the power of well-sampled early-time data and the need for immediate multiband, high-cadence follow-up for progress in understanding SNe Ia.

ID: 154620
Type: article
Authors: Villar, Victoria Ashley; Berger, Edo; Miller, G.; Chornock, R.; Rest, A.; Jones, D. O.; Drout, M. R.; Foley, R. J.; Kirshner, Robert; Lunnan, R.; Magnier, E.; Milisavljevic, D.; Sanders, N.; Scolnic, D.
Abstract: Photometric classification of supernovae (SNe) is imperative as recent and upcoming optical time-domain surveys, such as the Large Synoptic Survey Telescope (LSST), overwhelm the available resources for spectrosopic follow-up. Here we develop a range of light curve (LC) classification pipelines, trained on 513 spectroscopically classified SNe from the Pan-STARRS1 Medium-Deep Survey (PS1-MDS): 357 Type Ia, 93 Type II, 25 Type IIn, 21 Type Ibc, and 17 Type I superluminous SNe (SLSNe). We present a new parametric analytical model that can accommodate a broad range of SN LC morphologies, including those with a plateau, and fit this model to data in four PS1 filters (g _P1 r _P1 i _P1 z _P1). We test a number of feature extraction methods, data augmentation strategies, and machine- learning algorithms to predict the class of each SN. Our best pipelines result in ≈90% average accuracy, ≈70% average purity, and ≈80% average completeness for all SN classes, with the highest success rates for SNe Ia and SLSNe and the lowest for SNe Ibc. Despite the greater complexity of our classification scheme, the purity of our SN Ia classification, ≈95%, is on par with methods developed specifically for Type Ia versus non-Type Ia binary classification. As the first of its kind, this study serves as a guide to developing and training classification algorithms for a wide range of SN types with a purely empirical training set, particularly one that is similar in its characteristics to the expected LSST main survey strategy. Future work will implement this classification pipeline on ≈3000 PS1/MDS LCs that lack spectroscopic classification.

ID: 147045
Type: article
Authors: Rest, A.; Garnavich, P. M.; Khatami, D.; Kasen, D.; Tucker, B. E.; Shaya, E. J.; Olling, R. P.; Mushotzky, R.; Zenteno, A.; Margheim, S.; Strampelli, G.; James, D.; Smith, R. C.; Förster, F.; Villar, V. A.
Abstract: For decades, optical time-domain searches have been tuned to find ordinary supernovae, which rise and fall in brightness over a period of weeks. Recently, supernova searches have improved their cadences and a handful of fast-evolving luminous transients have been identified^1-5. These have peak luminosities comparable to type Ia supernovae, but rise to maximum in less than ten days and fade from view in less than one month. Here we present the most extreme example of this class of object thus far: KSN 2015K, with a rise time of only 2.2 days and a time above half-maximum of only 6.8 days. We show that, unlike type Ia supernovae, the light curve of KSN 2015K was not powered by the decay of radioactive elements. We further argue that it is unlikely that it was powered by continuing energy deposition from a central remnant (a magnetar or black hole). Using numerical radiation hydrodynamical models, we show that the light curve of KSN 2015K is well fitted by a model where the supernova runs into external material presumably expelled in a pre-supernova mass-loss episode. The rapid rise of KSN 2015K therefore probes the venting of photons when a hypersonic shock wave breaks out of a dense extended medium.

ID: 145759
Type: article
Authors: Scolnic, D.; Kessler, R.; Brout, D.; Cowperthwaite, P. S.; Soares-Santos, M.; Annis, J.; Herner, K.; Chen, H. -Y; Sako, M.; Doctor, Z.; Butler, R. E.; Palmese, A.; Diehl, H. T.; Frieman, J.; Holz, D. E.; Berger, E.; Chornock, R.; Villar, V. A.; Nicholl, M.; Biswas, R.; Hounsell, R.; Foley, R. J.; Metzger, J.; Rest, A.; García-Bellido, J.; Möller, A.; Nugent, P.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Davis, C.; Doel, P.; Drlica-Wagner, A.; Eifler, T. F.; Flaugher, B.; Fosalba, P.; Gaztanaga, E.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hartley, W. G.; Honscheid, K.; James, David J.; Johnson, M. W. G.; Johnson, M. D.; Krause, E.; Kuehn, K.; Kuhlmann, S.; Lahav, O.; Li, T. S.; Lima, M.; Maia, M. A. G.; March, M.; Marshall, J. L.; Menanteau, F.; Miquel, R.; Neilsen, E.; Plazas, A. A.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Smith, R. C.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, R. C.; Tucker, D. L.; Walker, A. R.; DES Collaboration
Abstract: The discovery of a kilonova (KN) associated with the Advanced LIGO (aLIGO)/Virgo event GW170817 opens up new avenues of multi-messenger astrophysics. Here, using realistic simulations, we provide estimates of the number of KNe that could be found in data from past, present, and future surveys without a gravitational-wave trigger. For the simulation, we construct a spectral time-series model based on the DES-GW multi-band light curve from the single known KN event, and we use an average of BNS rates from past studies of {10}³ {{Gpc}}^-3 {{yr}}^-1, consistent with the one event found so far. Examining past and current data sets from transient surveys, the number of KNe we expect to find for ASAS-SN, SDSS, PS1, SNLS, DES, and SMT is between 0 and 0.3. We predict the number of detections per future survey to be 8.3 from ATLAS, 10.6 from ZTF, 5.5/69 from LSST (the Deep Drilling/Wide Fast Deep), and 16.0 from WFIRST. The maximum redshift of KNe discovered for each survey is z=0.8 for WFIRST, z=0.25 for LSST, and z=0.04 for ZTF and ATLAS. This maximum redshift for WFIRST is well beyond the sensitivity of aLIGO and some future GW missions. For the LSST survey, we also provide contamination estimates from Type Ia and core-collapse supernovae: after light curve and template-matching requirements, we estimate a background of just two events. More broadly, we stress that future transient surveys should consider how to optimize their search strategies to improve their detection efficiency and to consider similar analyses for GW follow-up programs.