Title: Investigating the Unusual Spectroscopic Time Evolution in SN 2012fr

Abstract

The type Ia supernova (SN) 2012fr displayed a curious combination of its Si ii λλ5972, 6355 features. This includes the ratio of their pseudo-equivalent widths, placing it at the border of the shallow silicon (SS) and core normal (CN) spectral subtype in the Branch diagram, while the Si ii λ6355 expansion velocities place it as a high-velocity (HV) object in the Wang et al. spectral type that most intriguingly evolves slowly, placing it in the low-velocity gradient (LVG) typing of Benetti et al. Only 5% of SNe Ia are HV and located in the SS+CN portion of the Branch diagram, and fewer than 10% of SNe Ia are both HV and LVG. These features point toward SN 2012fr being quite unusual, similar in many ways to the peculiar SN 2000cx. We modeled the spectral evolution of SN 2012fr to see if we could gain some insight into its evolutionary behavior. We use the parameterized radiative transfer code SYNOW to probe the abundance stratification of SN 2012fr at pre-maximum, maximum, and post-maximum light epochs. We also use a grid of W7 models in the radiative transfer code PHOENIX to probe the effect of different density structures on the formation of themore » Si ii λ6355 absorption feature at post-maximum epochs. We find that the unusual features observed in SN 2012fr are likely due to a shell-like density enhancement in the outer ejecta. We report on possible reasons for atypical Ca ii absorption features, and suggest that they are related to the Si ii features.« less

Authors:

Cain, Christopher  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-9420-7384"

Baron, E.  ^[2];

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• Search DOE PAGES for ORCID "0000-0001-5393-1608"

Phillips, M. M.  ^[3];

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• Search DOE PAGES for ORCID "0000-0003-2734-0796"

Contreras, Carlos  ^[4];

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• Search DOE PAGES for ORCID "0000-0001-6293-9062"

Ashall, Chris  ^[5];

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• Search DOE PAGES for ORCID "0000-0002-5221-7557"

Stritzinger, Maximilian D.  ^[6];

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• Search DOE PAGES for ORCID "0000-0002-5571-1833"

Burns, Christopher R.  ^[7];

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• Search DOE PAGES for ORCID "0000-0003-4625-6629"

Piro, Anthony L.  ^[7];

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• Search DOE PAGES for ORCID "0000-0001-6806-0673"

Hsiao, Eric Y.  ^[8];

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Hoeflich, P.  ^[5];

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• Search DOE PAGES for ORCID "0000-0002-4338-6586"

Krisciunas, Kevin  ^[9];

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• Search DOE PAGES for ORCID "0000-0002-6650-694X"

Suntzeff, Nicholas B.  ^[9]

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• Search DOE PAGES for ORCID "0000-0002-8102-181X"

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+ Show Author Affiliations

1. Azusa Pacific Univ., CA (United States); Univ. of Oklahoma, Norman, OK (United States); Univ. of California, Riverside, CA (United States)
2. Univ. of Oklahoma, Norman, OK (United States); Univ. of Hamburg (Germany); Aarhus Univ. (Denmark)
3. Carnegie Observatories, La Serena (Chile). Las Campanas Observatory
4. Carnegie Observatories, La Serena (Chile). Las Campanas Observatory; Aarhus Univ. (Denmark)
5. Florida State Univ., Tallahassee, FL (United States)
6. Aarhus Univ. (Denmark)
7. Carnegie Observatories, Pasadena, CA (United States)
8. Carnegie Observatories, La Serena (Chile). Las Campanas Observatory; Aarhus Univ. (Denmark); Florida State Univ., Tallahassee, FL (United States)
9. Texas A & M Univ., College Station, TX (United States)

Publication Date:

Fri Dec 21 00:00:00 EST 2018

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of California, Oakland, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC); National Science Foundation (NSF); National Aeronautics and Space Administration (NASA); Aarhus University Research Fund (AUFF); Höchstleistungsrechenzentrum Nord (HLRN)

OSTI Identifier:

1544075

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

The Astrophysical Journal (Online)

Additional Journal Information:

Journal Name: The Astrophysical Journal (Online); Journal Volume: 869; Journal Issue: 2; Journal ID: ISSN 1538-4357

Publisher:

Institute of Physics (IOP)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; supernovae: general; supernovae: individual (2012fr)