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Abundance stratification in Type Ia supernovae - IV. The luminous, peculiar SN 1991T

Sasdelli, M and Mazzali, PA and Pian, E and Nomoto, K and Hachinger, S and Cappellaro, E and Benetti, S (2014) Abundance stratification in Type Ia supernovae - IV. The luminous, peculiar SN 1991T. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 445 (1). pp. 711-725. ISSN 0035-8711

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Abstract

The abundance distribution of the elements in the ejecta of the peculiar, luminous Type Ia supernova (SN Ia) 1991T is obtained modelling spectra from before maximum light until a year after the explosion, with the method of ‘Abundance Tomography’. SN 1991T is different from other slowly declining SNe Ia (e.g. SN 1999ee) in having a weaker Si II 6355 line and strong features of iron group elements before maximum. The distance to the SN is investigated along with the abundances and the density profile. The ionization transition that happens around maximum sets a strict upper limit on the luminosity. Both W7 and the WDD3 delayed detonation models are tested. WDD3 is found to provide marginally better fits. In this model the core of the ejecta is dominated by stable Fe with a mass of about 0.15 M⊙, as in most SNe Ia. The layer above is mainly 56Ni up to v ∼ 10 000 km s−1 (≈0.78 M⊙). A significant amount of 56Ni (∼3 per cent) is located in the outer layers. A narrow layer between 10 000 km s−1 and ∼12 000 km s−1 is dominated by intermediate-mass elements (IME), ∼0.18 M⊙. This is small for a SN Ia. The high luminosity and the consequently high ionization, and the high 56Ni abundance at high velocities, explain the peculiar early-time spectra of SN 1991T. The outer part is mainly of oxygen, ∼0.3 M⊙. Carbon lines are never detected, yielding an upper limit of 0.01 M⊙ for C. The abundances obtained with the W7 density model are qualitatively similar to those of the WDD3 model. Different elements are stratified with moderate mixing, resembling a delayed detonation.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical society following peer review. The version of record "Abundance stratification in Type Ia supernovae - IV. The luminous, peculiar SN 1991T" is available online at http://dx.doi.org/10.1093/mnras/stu1777
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: OXFORD UNIV PRESS
Related URLs:
Date Deposited: 08 Feb 2016 12:24
Last Modified: 08 Feb 2016 12:24
DOI or Identification number: 10.1093/mnras/stu1777
URI: http://researchonline.ljmu.ac.uk/id/eprint/2865

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