ASASSN-15pz: Revealing Significant Photometric Diversity Among 2009dc-like, Peculiar Type Ia Supernovae. (arXiv:1904.03198v1 [astro-ph.HE])

ASASSN-15pz: Revealing Significant Photometric Diversity Among 2009dc-like, Peculiar Type Ia Supernovae. (arXiv:1904.03198v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Chen_P/0/1/0/all/0/1">Ping Chen</a> (KIAA-PKU), <a href="http://arxiv.org/find/astro-ph/1/au:+Dong_S/0/1/0/all/0/1">Subo Dong</a> (KIAA-PKU), <a href="http://arxiv.org/find/astro-ph/1/au:+Katz_B/0/1/0/all/0/1">Boaz Katz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kochanek_C/0/1/0/all/0/1">C. S. Kochanek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kollmeier_J/0/1/0/all/0/1">Juna A. Kollmeier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maguire_K/0/1/0/all/0/1">K. Maguire</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Phillips_M/0/1/0/all/0/1">M. M. Phillips</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prieto_J/0/1/0/all/0/1">J. L. Prieto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shappee_B/0/1/0/all/0/1">B. J. Shappee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stritzinger_M/0/1/0/all/0/1">M. D. Stritzinger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bose_S/0/1/0/all/0/1">Subhash Bose</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brown_P/0/1/0/all/0/1">Peter J. Brown</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Holoien_T/0/1/0/all/0/1">T. W.-S. Holoien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Galbany_L/0/1/0/all/0/1">L. Galbany</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Milne_P/0/1/0/all/0/1">Peter A. Milne</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morrell_N/0/1/0/all/0/1">Nidia Morrell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Piro_A/0/1/0/all/0/1">Anthony L. Piro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stanek_K/0/1/0/all/0/1">K. Z. Stanek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thompson_T/0/1/0/all/0/1">Todd A. Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Young_D/0/1/0/all/0/1">D. R. Young</a>

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) from pre-peak
to nebular phases, but it has a peak luminosity M_B,peak = -19.69 +/- 0.12 mag
that is approx 0.6 mag dimmer than SN 2009dc and is comparable to the SN 1991T
sub-class of SNe Ia located at the luminous end of the width-luminosity
relation. The synthesized Ni56 mass of M_Ni56 = 1.13 +/- 0.14 M_sun is also
substantially less than several 2009dc-like SNe. Previous well-studied
2009dc-like SNe have generally suffered from large and uncertain host-galaxy
extinction, which is negligible for ASASSN-15pz. The post-peak (B-V) color
curves of SN 2009dc and ASASSN-15pz have essentially identical slopes, based on
which we estimate the host selective extinction of SN 2009dc (E(B-V)_host=0.12
mag) and confirm the high luminosity of SN 2009dc (M_B, peak[2009dc] approx
-20.3 mag). The 2009dc-like SN population, whose rate is on the order of ~1%
relative to SNe Ia, exhibit 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 d) decline rates. The nebular-phase
spectra provide powerful diagnostics to identify the 2009dc-like events as a
distinct class from SNe Ia and other SNe Ia-pec. To refer to this class, we
suggest 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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