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

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

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 Chandrasekharmass 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.

Line: Profiles, Supernovae: General, Techniques: Spectroscopic
0035-8711
3567-3582
Maguire, K.
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Sim, S. A.
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Shingles, L.
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Spyromilio, J.
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Jerkstrand, A.
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Sullivan, M.
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Chen, T. W.
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Cartier, R.
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Dimitriadis, G.
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Frohmaier, C.
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Galbany, L.
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Gutiérrez, C. P.
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Hosseinzadeh, G.
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A. Howell, D.
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Inserra, C.
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Rudy, R.
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Sollerman, J.
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Maguire, K.
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Sim, S. A.
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Shingles, L.
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Spyromilio, J.
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Jerkstrand, A.
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Sullivan, M.
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Chen, T. W.
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Cartier, R.
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Dimitriadis, G.
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Frohmaier, C.
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Galbany, L.
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Gutiérrez, C. P.
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Hosseinzadeh, G.
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A. Howell, D.
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Inserra, C.
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Rudy, R.
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Sollerman, J.
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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., A. Howell, D., Inserra, C., 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), 3567-3582. (doi:10.1093/mnras/sty820).

Record type: Article

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 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 Chandrasekharmass 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.

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Using late-time optical and near-infrared spectra to constrain Type Ia supernova explosion properties - Accepted Manuscript
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Accepted/In Press date: 26 March 2018
e-pub ahead of print date: 30 March 2018
Published date: 1 July 2018
Keywords: Line: Profiles, Supernovae: General, Techniques: Spectroscopic

Identifiers

Local EPrints ID: 421701
URI: https://eprints.soton.ac.uk/id/eprint/421701
ISSN: 0035-8711
PURE UUID: cc4e78b5-2df1-4b36-a314-a1c49705b1ce
ORCID for M. Sullivan: ORCID iD orcid.org/0000-0001-9053-4820
ORCID for C. Inserra: ORCID iD orcid.org/0000-0002-3968-4409

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Date deposited: 21 Jun 2018 16:30
Last modified: 17 Jul 2019 00:38

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