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Published December 11, 2015 | Published
Journal Article Open

Spectral models for early time SN 2011fe observations

Abstract

We use observed UV through near-IR spectra to examine whether SN 2011fe can be understood in the framework of Branch-normal Type Ia supernovae (SNe Ia) and to examine its individual peculiarities. As a benchmark, we use a delayed-detonation model with a progenitor metallicity of Z_⊙/20. We study the sensitivity of features to variations in progenitor metallicity, the outer density profile, and the distribution of radioactive nickel. The effect of metallicity variations in the progenitor have a relatively small effect on the synthetic spectra. We also find that the abundance stratification of SN 2011fe resembles closely that of a delayed-detonation model with a transition density that has been fit to other Branch-normal SNe Ia. At early times, the model photosphere is formed in material with velocities that are too high, indicating that the photosphere recedes too slowly or that SN 2011fe has a lower specific energy in the outer ≈0.1 M_⊙ than does the model. We discuss several explanations for the discrepancies. Finally, we examine variations in both the spectral energy distribution and in the colours due to variations in the progenitor metallicity, which suggests that colours are only weak indicators for the progenitor metallicity, in the particular explosion model that we have studied. We do find that the flux in the U band is significantly higher at maximum light in the solar metallicity model than in the lower metallicity model and the lower metallicity model much better matches the observed spectrum.

Additional Information

© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 August 20. Received 2015 August 19; in original form 2015 May 8. First published online October 13, 2015. We thank Aaron Dotter for help in constructing the synthetic photometry with a wide choice of filters. We also thank the anonymous referee for improving the presentation of this work. The work has been supported in part by support for programmes HST-GO-12298.05-A, and HST-GO-12948.04-A was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. This work was also supported in part by the NSF, AST-0709181, AST-0707704, AST-0708855, AST-0708873. This research was also supported, in part, by the NSF grant AST-0703902 to PAH. The work of EB was also supported in part by SFB 676, GRK 1354 from the DFG. ID has been supported in part by the Spanish Ministry of Science and Innovation project AYA2008-04211-C02-02 (ID). This research used resources of the National Energy Research Scientific Computing Center (NERSC), which is supported by the Office of Science of the US Department of Energy under Contract No. DE-AC02-05CH11231; and the Höchstleistungs Rechenzentrum Nord (HLRN). We thank both these institutions for a generous allocation of computer time.

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August 22, 2023
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