Type Ia Supernovae Strongly Interacting with Their Circumstellar Medium

Creators: Silverman, Jeffrey M.; Cao, Yi; Horesh, Assaf; Kulkarni, Shrinivas R.; Kasliwal, M. M.

Abstract

Owing to their utility for measurements of cosmic acceleration, Type Ia supernovae (SNe Ia) are perhaps the best-studied class of SNe, yet the progenitor systems of these explosions largely remain a mystery. A rare subclass of SNe Ia shows evidence of strong interaction with their circumstellar medium (CSM), and in particular, a hydrogen-rich CSM; we refer to them as SNe Ia-CSM. In the first systematic search for such systems, we have identified 16 SNe Ia-CSM, and here we present new spectra of 13 of them. Six SNe Ia-CSM have been well studied previously, three were previously known but are analyzed in depth for the first time here, and seven are new discoveries from the Palomar Transient Factory. The spectra of all SNe Ia-CSM are dominated by Hα emission (with widths of ~2000 km s^(–1)) and exhibit large Hα/Hβ intensity ratios (perhaps due to collisional excitation of hydrogen via the SN ejecta overtaking slower-moving CSM shells); moreover, they have an almost complete lack of He I emission. They also show possible evidence of dust formation through a decrease in the red wing of Hα 75-100 days past maximum brightness, and nearly all SNe Ia-CSM exhibit strong Na I D absorption from the host galaxy. The absolute magnitudes (uncorrected for host-galaxy extinction) of SNe Ia-CSM are found to be –21.3 mag ≤ M_R ≤ –19 mag, and they also seem to show ultraviolet emission at early times and strong infrared emission at late times (but no detected radio or X-ray emission). Finally, the host galaxies of SNe Ia-CSM are all late-type spirals similar to the Milky Way, or dwarf irregulars like the Large Magellanic Cloud, which implies that these objects come from a relatively young stellar population. This work represents the most detailed analysis of the SN Ia-CSM class to date.

Additional Information

© 2013 The American Astronomical Society. Received 2013 March 29; accepted 2013 April 26; published 2013 June 14. We thank K. Alatalo, T. Barlow, E. Bellm, B. Cobb, A. Cucchiara, M. Ganeshalingam, Y. Green, M. Hidas, L. Kewley, N. Konidaris, S. Lazarevic, N. Lee, D. Levitan, M. McCourt, K. Mooley, R. Mostardi, D. Perley, A. G. Riess, B. Sesar, R. Street, T. Treu, V. Viscomi, and X. Wang for their assistance with some of the observations and data reduction; B. Dilday, O. Fox, and L. Wang for helpful discussions; and D. Balam, M. Stritzinger, J. Vinko, and J. C. Wheeler for providing unpublished spectra of possible SNe Ia-CSM. We are grateful to the staffs at the Isaac Newton Group of Telescopes and the Lick, Keck, Palomar, and Kitt Peak National Observatories for their support. 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 the National Aeronautics and Space Administration (NASA); the observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community; we are most fortunate to have the opportunity to conduct observations from this mountain. 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 NASA. Funding for SDSSIII has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSSIII Web site is http://www.sdss3.org/. Supernova research by A.V.F.'s group at UC Berkeley is supported by Gary and Cynthia Bengier, the Richard and Rhoda Goldman Fund, the Christopher R. Redlich Fund, the TABASGO Foundation, and NSF grants AST-0908886 and AST-1211916. Work by A.G.-Y. and his group is supported by grants from the ISF, BSF, GIF, Minerva, an FP7/ERC grant, and the Helen and Martin Kimmel Award for Innovative Investigation. M.M.K. acknowledges generous support from a Hubble Fellowship and a Carnegie-Princeton Fellowship.

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