The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode as Deflagrations?

Abstract

We present extensive u'g'r'i'BVRIYJHKs photometry and optical spectroscopy of SN 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called ``the most peculiar known type Ia supernova.'' Both supernovae exhibited high ionization SN 1991T-like pre-maximum spectra, yet low peak luminosities like SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roughly half those of typical type Ia supernovae. The R and I light curves of both supernovae were also peculiar in not displaying the secondary maximum observed for normal type Ia supernovae. Our YJH photometry of SN 2005hk reveals the same peculiarity in the near-infrared. By combining our optical and near-infrared photometry of SN 2005hk with published ultraviolet light curves obtained with the Swift satellite, we are able to construct a bolometric light curve from ~10 days before to ~60 days after B maximum. The shape and unusually low peak luminosity of this light curve, plus the low expansion velocities and absence of a secondary maximum at red and near-infrared wavelengths, are all in reasonable agreement with model calculations of a 3D deflagration which produces ~0.25 M_sun of 56Ni.

Accepted by PASP, to appear in April 2007 issue, 63 pages, 16 figures, 11 tables

Cited by in corpus (11)

• CfA3: 185 Type Ia Supernova Light Curves from the CfA
• Determining the Type, Redshift, and Age of a Supernova Spectrum
• The Sloan Digital Sky Survey-II Supernova Survey: Technical Summary
• Spectropolarimetry of Supernovae
• The Sloan Digital Sky Survey-II Supernova Survey: Search Algorithm and Follow-up Observations
• Type Ia Supernovae are Good Standard Candles in the Near Infrared: Evidence from PAIRITEL
• Ultraviolet Spectroscopy of Supernovae: The First Two Years of Swift Observations
• First-Year Spectroscopy for the SDSS-II Supernova Survey
• Diversity of supernovae Ia determined using equivalent widths of Si II 4000
• Supernovae and Cosmology
• Physics of Supernovae: theory, observations, unresolved problems