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

Maguire, K, Sim, S A, Shingles, L, Spyromilio, J, Jerkstrand, A, Sullivan, M, Chen, T-W, Cartier, R, Dimitriadis, G, Frohmaier, C, Galbany, L, Gutiérrez, C P, Hosseinzadeh, G, Howell, D A, Inserra, C ORCID:, Rudy, R and Sollerman, J 2018. Using late-time optical and near-infrared spectra to constrain Type Ia supernova explosion properties. Monthly Notices of the Royal Astronomical Society 477 (3) , pp. 3567-3582. 10.1093/mnras/sty820

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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 focusing on [Fe ii] and [Ni ii] emission lines in the ∼7000–7500 Å 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 ionized [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 Å 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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 2 January 2019
Date of Acceptance: 26 March 2018
Last Modified: 05 May 2023 02:09

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