@article{c1341ff5e9be4c508fd47af12edc2b4f,
title = "Late-time spectroscopy of Type Iax Supernovae",
abstract = "We examine the late-time (t≳200 d after peak brightness) spectra of Type Iax supernovae (SNe Iax), a low-luminosity, low-energy class of thermonuclear stellar explosions observationally similar to, but distinct from, Type Ia supernovae. We present new spectra of SN 2014dt, resulting in the most complete late-time spectral sequence of an SN Iax. At late times, SNe Iax have generally similar spectra, all with a similar continuum shape and strong forbiddenline emission. However, there is also significant diversity where some SN Iax spectra display narrow P-Cygni features from permitted lines and a continuum indicative of a photosphere at late times in addition to strong narrow (FWHM < 3500 km s-1) forbidden lines, others have no obvious P-Cygni features, strong broad (FWHM > 6000 km s-1) forbidden lines, and weak narrow forbidden lines, and some SNe Iax have spectra intermediate to these two varieties. We find that SNe Iax with strong broad forbidden lines are more luminous and have higher velocity ejecta at peak brightness. We estimate blackbody and kinematic radii of the late-time photosphere, finding the latter significantly larger than the former. We propose a two-component model that solves this discrepancy and explains the diversity of the late-time spectra of SNe Iax. In this model, the broad forbidden lines originate from the SN ejecta, while the photosphere, P-Cygni lines, and narrow forbidden lines originate from a wind launched from the remnant of the progenitor white dwarf and is driven by the radioactive decay of newly synthesized material left in the remnant. The relative strength of the two components accounts for the diversity of late-time SN Iax spectra. This model also solves the puzzle of a long-lived photosphere and the slow late-time decline of SNe Iax.",
keywords = "PTF09eiy, PTF10bvr, SN 2002cx, SN 2004cs, SN 2005P, SN 2005hk, SN 2007J, SN 2008A, SN 2008ge, SN 2008ha, SN 2010ae, SN 2011ay, SN 2011ce, SN 2012Z, SN 2014dt, Supernovae: general, Supernovae: individual: PTF09ego",
author = "Foley, {Ryan J.} and Jha, {Saurabh W.} and Pan, {Yen Chen} and Zheng, {Wei Kang} and Lars Bildsten and Filippenko, {Alexei V.} and Daniel Kasen",
note = "Funding Information: ACKNOWLEDGEMENTS RJF gratefully acknowledges support from NSF grantAST-1518052 and the Alfred P. Sloan Foundation. SN Iax research at Rutgers University is supported by NASA/HST grants GO-12913 and GO-12973 to SWJ. This work was supported by the NSF under grants PHY 11-25915 and AST 11-09174. AVF's research was funded by NSF grant AST-1211916, the TABASGO Foundation, and the Christopher R. Redlich Fund. We thank the participants of the 'Fast and Furious: Understanding Exotic Astrophysical Transients' workshop at the Aspen Center for Physics, which is supported in part by the NSF under grant PHY-1066293. Some of the work presented in this manuscript was initiated there during discussions with L. Bildsten and D. Kasen. Portions of this manuscript were also written during the Aspen Center for Physics workshop, 'The Dynamic Universe: Understanding ExaScale Astronomical Synoptic Surveys'. We are grateful to the Aspen Center for Physics for its hospitality during the 'Fast and Furious' and 'Dynamic Universe' workshops in 2014 June and 2015 May, respectively. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). Based in part on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Minist{\'e}rio da Ci{\^e}ncia, Tecnologia, e Inova{\c c}{\u a}o (MCTI) da Rep{\'u}blica Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, theNSF, the University of California, the Sylvia&Jim Katzman Foundation, and the TABASGO Foundation. Research at Lick Observatory is partially supported by a generous gift from Google. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the observatory was made possible by the generous financial support of the W. M. Keck Foundation. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W.M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with NASA. We thank the staffs of the various observatories and telescopes (SOAR, Keck, SALT, Lick) where data were obtained, as well as observers who helped obtain some of the data (see Table A2). Facility: SOAR (Goodman), Keck:I (LRIS), Shane (Kast Double spectrograph), SALT (RSS). Publisher Copyright: {\textcopyright} 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.",
year = "2016",
month = sep,
day = "1",
doi = "10.1093/mnras/stw1320",
language = "English (US)",
volume = "461",
pages = "433--457",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "1",
}