Evidence for spectropolarimetric diversity in type Ia supernovae

Douglas C. Leonard*, L. I. Weidong, Alexei V. Filippenko, Ryan J. Foley, Ryan Chornock

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

101 Scopus citations

Abstract

We present single-epoch, postmaximum spectropolarimetry of four Type Ia supernovae (SNe Ia) that span a range of spectral and photometric properties: SN 2002bf and SN 2004dt exhibit unusually high-velocity (HV) absorption lines. SN 1997dt is probably somewhat subluminous, and SN 2003du is slightly overluminous. We detect polarization modulations across strong lines in all four objects, demonstrating that all are intrinsically polarized. However, the nature and degree of the polarization varies considerably. Including all SNe Ia studied thus far, the following order emerges in terms of increasing strength of line-polarization features: ordinary/overluminous < subluminous < HV SNe Ia, with the strength of the line-polarization features increasing from 0.2% in the slightly overluminous SN 2003du to 2% in both of the HV SNe la in our study. The most convincing explanation for the line polarization of all objects is partial obscuration of the photosphere by clumps of intermediate-mass elements forged in the explosion; the polarization characteristics of the HV SNe Ia in particular effectively rule out a simple ellipsoidal asphericity as the root cause of their line polarization. That SNe la are separable into different groups based on their spectropolarimetric characteristics may help narrow down progenitor possibilities and/or explosion physics. In particular, the recently proposed gravitationally confined detonation model may provide an attractive explanation for many of the observed polarization characteristics of HV SNe Ia.

Original languageEnglish (US)
Pages (from-to)450-475
Number of pages26
JournalAstrophysical Journal
Volume632
Issue number1 I
DOIs
StatePublished - Oct 10 2005
Externally publishedYes

Keywords

  • Supernovae: individual (SN 1997dt, SN 2002bf, SN 2003du, SN 2004dt)
  • Techniques: polarimetric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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