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An Intermediate Type Ia Supernova Between Normal And Super-Chandrasekhar

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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Contributor : Dominique Girod <>
Submitted on : Tuesday, June 28, 2016 - 10:27:10 AM
Last modification on : Friday, September 10, 2021 - 1:50:15 PM

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Yi Cao, J. Johansson, Peter E. Nugent, A. Goobar, Jakob Nordin, et al.. An Intermediate Type Ia Supernova Between Normal And Super-Chandrasekhar. The Astrophysical Journal, American Astronomical Society, 2016, 823, pp.147. ⟨10.3847/0004-637X/823/2/147⟩. ⟨in2p3-01338216⟩



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