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arXiv · 1601.00686

An Intermediate Type Ia Supernova Between Normal And Super-Chandrasekhar

Yi Cao·J. Johansson·Peter E. Nugent·A. Goobar·Jakob Nordin·S. R. Kulkarni·S. Bradley Cenko·Ori Fox·Mansi M. Kasliwal·C. Fremling·R. Amanullah·E. Y. Hsiao·D. A. Perley·Brian D. Bue·Frank J. Masci·William H. Lee·Nicolas Chotard
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Abstract

In this paper, we report observations of a peculiar Type Ia supernova iPTF13asv (a.k.a., SN2013cv) from the onset of the explosion to months after its peak. The early-phase spectra of iPTF13asv show absence of iron absorption, indicating that synthesized iron elements are confined to low-velocity regions of the ejecta, which, in turn, implies a stratified ejecta structure along the line of sight. Our analysis of iPTF13asv's light curves and spectra shows that it is an intermediate case between normal and super-Chandrasekhar events. On the one hand, its light curve shape (B-band $\Delta m_{15}=1.03\pm0.01$) and overall spectral features resemble those of normal Type Ia supernovae. On the other hand, similar to super-Chandrasekhar events, it shows large peak optical and UV luminosity ($M_B=-19.84\,\rm{mag}$, $M_{uvm2}=-15.5\,\rm{mag}$) a relatively low but almost constant \ion{Si}{2} velocities of about $10,000\,\rm{km}\,\rm{s}^{-1}$, and persistent carbon absorption in the spectra. We estimate a $^{56}$Ni mass of $0.81^{+0.10}_{-0.18}M_\odot$ and a total ejecta mass of $1.59^{+0.45}_{-0.12}M_\odot$. The large ejecta mass of iPTF13asv and its stratified ejecta structure together seemingly favor a double-degenerate origin.

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Yi Cao, J. Johansson, Peter E. Nugent, A. Goobar, Jakob Nordin, S. R. Kulkarni, S. Bradley Cenko, Ori Fox, Mansi M. Kasliwal, C. Fremling, R. Amanullah, E. Y. Hsiao, D. A. Perley, Brian D. Bue, Frank J. Masci, William H. Lee, Nicolas Chotard. 2016-01-04. An Intermediate Type Ia Supernova Between Normal And Super-Chandrasekhar. https://doi.org/10.3847/0004-637x/823/2/147

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