Ultraviolet, optical, and X-ray observations of the type Ia supernova 2005am with Swift

Abstract

We present ultraviolet and optical light curves in six broadband filters and grism spectra obtained by Swift's Ultraviolet/Optical Telescope for the Type Ia supernova SN 2005am. The data were collected beginning about 4 days before the B-band maximum, with excellent coverage of the rapid decline phase and later observations extending out to 69 days after the peak. The optical and near-UV light curve match well those of SN 1992A. The other UV observations constitute the first set of light curves shorter than 2500 angstrom and allow us to compare the light curve evolution in three UV bands. One interesting feature is that the decay in the intermediate UVM2 band is shallower than in the filters on either side and may result from the bump in the interstellar extinction curve. The UV behavior of this and other low-redshift supernovae can be used to constrain theories of progenitor evolution or to interpret optical light curves of high-redshift supernovae. Using Swift's X-Ray Telescope, we also report the upper limit to SN 2005am's X-ray luminosity to be 6 x 10(39) ergs s(-1) in the 0.3 - 10 keV. This result is derived from 58 ks of exposure time spread out over 7 weeks beginning 4 days before the B-band maximum.