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Using late-time optical and near-infrared spectra to constrain Type Ia supernova explosion properties

Authors :
Maguire, K.
Sim, S. A.
Shingles, L.
Spyromilio, J.
Jerkstrand, A.
Sullivan, M.
Chen, T. -W.
Cartier, R.
Dimitriadis, G.
Frohmaier, C.
Galbany, L.
GutiƩrrez, C. P.
Hosseinzadeh, G.
Howell, D. A.
Inserra, C.
Rudy, R.
Sollerman, J.
Publication Year :
2018

Abstract

The late-time spectra of Type Ia supernovae (SNe Ia) are powerful probes of the underlying physics of their explosions. We investigate the late-time optical and near-infrared spectra of seven SNe Ia obtained at the VLT with XShooter at $>$200 d after explosion. At these epochs, the inner Fe-rich ejecta can be studied. We use a line-fitting analysis to determine the relative line fluxes, velocity shifts, and line widths of prominent features contributing to the spectra ([Fe II], [Ni II], and [Co III]). By focussing on [Fe II] and [Ni II] emission lines in the ~7000-7500 \AA\ region of the spectrum, we find that the ratio of stable [Ni II] to mainly radioactively-produced [Fe II] for most SNe Ia in the sample is consistent with Chandrasekhar-mass delayed-detonation explosion models, as well as sub-Chandrasekhar mass explosions that have metallicity values above solar. The mean measured Ni/Fe abundance of our sample is consistent with the solar value. The more highly ionised [Co III] emission lines are found to be more centrally located in the ejecta and have broader lines than the [Fe II] and [Ni II] features. Our analysis also strengthens previous results that SNe Ia with higher Si II velocities at maximum light preferentially display blueshifted [Fe II] 7155 \AA\ lines at late times. Our combined results lead us to speculate that the majority of normal SN Ia explosions produce ejecta distributions that deviate significantly from spherical symmetry.<br />Comment: 17 pages, 12 figure, accepted for publication in MNRAS

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.1803.10252
Document Type :
Working Paper
Full Text :
https://doi.org/10.1093/mnras/sty820