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

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    • K. Maguire
    • S. A. Sim
    • L. Shingles
    • J. Spyromilio
    • A. Jerkstrand
    • M. Sullivan
    • T.-W. Chen
    • R. Cartier
    • G. Dimitriadis
    • C. Frohmaier
    • L. Galbany
    • C. P. Gutiérrez
    • G. Hosseinzadeh
    • D. A. Howell
    • C. Inserra
    • R. Rudy
    • J. Sollerman

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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 focussing 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 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 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.

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    Original languageEnglish
    JournalMonthly Notices of the Royal Astronomical Society
    Journal publication date30 Mar 2018
    Early online date30 Mar 2018
    DOIs
    StateEarly online date - 30 Mar 2018

      Research areas

    • supernovae: general, techniques: spectroscopic, line: profiles

    ID: 149061175