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On the source of the dust extinction in type Ia supernovae and the discovery of anomalously strong Na i absorption

Phillips, MM and Simon, JD and Morrell, N and Burns, CR and Cox, NLJ and Foley, RJ and Karakas, AI and Patat, F and Sternberg, A and Williams, RE and Gal-Yam, A and Hsiao, EY and Leonard, DC and Persson, SE and Stritzinger, M and Thompson, IB and Campillay, A and Contreras, C and Folatelli, G and Freedman, WL and Hamuy, M and Roth, M and Shields, GA and Suntzeff, NB and Chomiuk, L and Ivans, II and Madore, BF and Penprase, BE and Perley, DA and Pignata, G and Preston, G and Soderberg, AM (2013) On the source of the dust extinction in type Ia supernovae and the discovery of anomalously strong Na i absorption. The Astrophysical Journal, 779 (1). ISSN 1538-4357

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Abstract

High-dispersion observations of the Na I D λλ5890, 5896 and K I λλ7665, 7699 interstellar lines, and the diffuse interstellar band at 5780 Å in the spectra of 32 Type Ia supernovae are used as an independent means of probing dust extinction. We show that the dust extinction of the objects where the diffuse interstellar band at 5780 Å is detected is consistent with the visual extinction derived from the supernova colors. This strongly suggests that the dust producing the extinction is predominantly located in the interstellar medium of the host galaxies and not in circumstellar material associated with the progenitor system. One quarter of the supernovae display anomalously large Na I column densities in comparison to the amount of dust extinction derived from their colors. Remarkably, all of the cases of unusually strong Na I D absorption correspond to "Blueshifted" profiles in the classification scheme of Sternberg et al. This coincidence suggests that outflowing circumstellar gas is responsible for at least some of the cases of anomalously large Na I column densities. Two supernovae with unusually strong Na I D absorption showed essentially normal K I column densities for the dust extinction implied by their colors, but this does not appear to be a universal characteristic. Overall, we find the most accurate predictor of individual supernova extinction to be the equivalent width of the diffuse interstellar band at 5780 Å, and provide an empirical relation for its use. Finally, we identify ways of producing significant enhancements of the Na abundance of circumstellar material in both the single-degenerate and double-degenerate scenarios for the progenitor system. © 2013. The American Astronomical Society. All rights reserved..

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society
Date Deposited: 18 May 2017 08:23
Last Modified: 11 Sep 2017 22:39
DOI or Identification number: 10.1088/0004-637X/779/1/38
URI: http://researchonline.ljmu.ac.uk/id/eprint/6458

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