ASASSN-15pz: Revealing Significant Photometric Diversity among 2009dc-like, Peculiar SNe Ia

Ping Chen, Subo Dong, Boaz Katz, C. S. Kochanek, Juna A. Kollmeier, K. Maguire, M. M. Phillips, J. L. Prieto, B. J. Shappee, M. D. Stritzinger, Subhash Bose, Peter J. Brown, T. W-S Holoien, L. Galbany, Peter A. Milne, Nidia Morrell, Anthony L. Piro, K. Z. Stanele, Todd A. Thompson, D. R. Young

Research output: Contribution to journalArticlepeer-review

Abstract

We report comprehensive multi-wavelength observations of a peculiar Type Ia-like supernova ("SN Ia-pec") ASASSN-15pz. ASASSN-15pz is a spectroscopic "twin" of SN 2009dc, a so-called "Super-Chandrasekhar-mass" SN, throughout its evolution, but it has a peak luminosity M-B,(peak) = -19.69 +/- 0.12 mag that is approximate to 0.6 mag dimmer and comparable to the SN 1991T sub-class of SNe Ia at the luminous end of the normal width-luminosity relation. The synthesized Ni-56 mass of M-56Ni = 1.13 +/- 0.14 M-circle dot is also substantially less than that found for several 2009dc-like SNe. Previous well-studied 2009dc-like SNe have generally suffered from large and uncertain amounts of host-galaxy extinction, which is negligible for ASASSN-15pz. Based on the color of ASASSN-15pz, we estimate a host extinction for SN 2009dc of E(B - V)(host) = 0.12 mag and confirm its high luminosity (M-B,(peak) [2009dc] approximate to -20.3 mag). The 2009dc-like SN population, which represents similar to 1% of SNe Ia, exhibits a range of peak luminosities, and do not fit onto the tight width-luminosity relation. Their optical light curves also show significant diversity of late-time (greater than or similar to 50 days) decline rates. The nebular-phase spectra provide powerful diagnostics to identify the 2009dc-like events as a distinct class of SNe Ia. We suggest referring to these sources using the phenomenology-based "2009dc-like SN Ia-pec" instead of "Super-Chandrasekhar SN Ia," which is based on an uncertain theoretical interpretation.

Original languageEnglish
Article number35
Number of pages16
JournalAstrophysical Journal
Volume880
Issue number1
DOIs
StatePublished - 20 Jul 2019

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