Spectropolarimetry of extremely luminous type Ia supernova 2009dc: Nearly spherical explosion of super-chandrasekhar mass white dwarf

Masaomi Tanaka, Koji S. Kawabata, Masayuki Yamanaka, Keiichi Maeda, Takashi Hattori, Kentaro Aoki, Ken'Ichi Nomoto, Masanori Iye, Toshiyuki Sasaki, Paolo A. Mazzali, Elena Pian

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57 Citations (Scopus)

Abstract

We present the first spectropolarimetric observations of a candidate of super-Chandrasekhar mass Type Ia supernova (SN): SN 2009dc. The observations were performed at 5.6 and 89.5 days after the B-band maximum. The data taken at the later epoch are used to determine the interstellar polarization. Continuum polarization is found to be small (<0.3%), indicating that the explosion is nearly spherically symmetric. This fact suggests that a very aspherical explosion is not a likely scenario for SN 2009dc. Polarization at the Si II and Ca II lines clearly shows a loop in the Q-U plane, indicating a non-axisymmetric, clumpy distribution of intermediate-mass elements. The degree of line polarization at the Si and Ca lines is moderate (0.5% 0.1% and 0.7% 0.1%, respectively), but it is higher than expected from the trend of other TypeIaSNe. This may suggest that there are thick enough, clumpy Si-rich layers above the thick 56Ni-rich layers (≳1.2 M). The observed spectropolarimetric properties, combined with the photometric and spectroscopic properties, suggest that the progenitor of SN 2009dc has a super-Chandrasekhar mass, and that the explosion geometry is globally spherically symmetric, with clumpy distribution of intermediate-mass elements.

Original languageEnglish
Pages (from-to)1209-1216
Number of pages8
JournalAstrophysical Journal
Volume714
Issue number2
DOIs
Publication statusPublished - 2010 Jan 1
Externally publishedYes

Keywords

  • Polarization
  • Supernovae: general
  • Supernovae: individual (SN 2009dc, SNe 2003fg, 2006gz, 1991T)
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Tanaka, M., Kawabata, K. S., Yamanaka, M., Maeda, K., Hattori, T., Aoki, K., Nomoto, KI., Iye, M., Sasaki, T., Mazzali, P. A., & Pian, E. (2010). Spectropolarimetry of extremely luminous type Ia supernova 2009dc: Nearly spherical explosion of super-chandrasekhar mass white dwarf. Astrophysical Journal, 714(2), 1209-1216. https://doi.org/10.1088/0004-637X/714/2/1209