We present extensive u'g'r'i'BVRIYJHKs photometry and optical spectroscopy of the Type Ia supernova (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 premaximum spectra, yet low peak luminosities like that of 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 ~15 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 three-dimensional deflagration that produces ~0.2 Msolar of 56Ni.Based in part on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium. Partly based on observations collected at the European Southern Observatory, Chile, in the course of program 076.A-0156.
Publications of the Astronomical Society of the Pacific
- Pub Date:
- April 2007
- supernovae: individual (SN 2005hk);
- Accepted by PASP, to appear in April 2007 issue, 63 pages, 16 figures, 11 tables