SOUSA: the Swift Optical Ultraviolet Supernova Archive

Swift

Optical

Ultraviolet

Supernova

Archive

SOUSA is an archive-in-the-making of all of the Swift supernova data.  In its final form, it will contain the images and intermediate photometry products as well as the final photometry.  To begin with, we are providing the revised photometry of SNe we've already published onto the updated photometric calibration.    More SNe will be updated as we go.  The paper describing the photometric reduction will be published in Astrophysics and Space Science and is available on astro-ph.

One use of the data we already have is improving what we do with Swift/UVOT during the rest of its lifetime.  Some of the plots in the paper should be useful for proposing new SNe for observation with Swift or preparing Guest Investigator proposals.  For example, the plot below gives a rough idea of the brightness of SNe in the mid-ultraviolet.  This allows one to estimate the distance to which one could detect a SN down to a given limiting magnitude.  The right axis of the plot gives the distance modulus for a limiting magnitude of uvm2=20.

 The limiting magnitude UVOT reaches is a function of the exposure time and the brightness of the underlying galaxy (due to our conservative method of subtracting the galaxy flux and propagating its uncertainty into the final photometry and limits).   For low contamination, 1000 seconds will reach a limiting magnitude of 20.  Based on the exposure time ratios for the preferred UVOT mode 0x223f, 3000 seconds of exposure are needed for the full 6 filters.

 

This plot shows the color and absolute magnitude evolution for a well observed supernova of most subclasses.  This could be used to estimate the class and/or epoch of a SN with UV/optical photometry.  The plots could also be helpful in planning what epochs could be reached to a given limiting magnitude.