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arXiv · 1904.03198

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. Stanek·Todd A. Thompson·D. R. Young
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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 \approx 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 Ni56 mass of M_Ni56 = 1.13 +/- 0.14 M_sun 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] \approx -20.3 mag). The 2009dc-like SN population, which represents ~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 (>~ 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.

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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. Stanek, Todd A. Thompson, D. R. Young. 2019-04-05. ASASSN-15pz: Revealing Significant Photometric Diversity among 2009dc-like, Peculiar SNe Ia. https://doi.org/10.3847/1538-4357%2Fab2630

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