2010ApJ...714.1209T -
Astrophys. J., 714, 1209-1216 (2010/May-2)
Spectropolarimetry of extremely luminous type Ia supernova 2009dc: nearly spherical explosion of super-chandrasekhar mass white dwarf.
TANAKA M., KAWABATA K.S., YAMANAKA M., MAEDA K., HATTORI T., AOKI K., NOMOTO K., IYE M., SASAKI T., MAZZALI P.A. and PIAN E.
Abstract (from CDS):
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 Type Ia SNe. 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.
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Journal keyword(s):
polarization - supernovae: general - supernovae: individual (SN 2009dc, SN 2003fg, SN 2006gz, SN 1991T) - white dwarfs
Simbad objects:
17
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