Swift and SIRAH: UV to NIR observations of Type Ia Supernovae Beyond the Twilight Zone

Abstract

While Swift observations have uncovered a large diversity in the UV luminosities of Type Ia Supernovae (SNe Ia), the physical origin of the diversity of these standard candles and the cosmological impact is still unknown. We propose to observe a sample of twenty-four Type Ia Supernovae (SNe Ia) in the nearby Hubble flow with Swift’s Ultra-Violet/Optical Telescope (UVOT). In coordination with the Hubble Space Telescope’s (HST) SIRAH program, these SNe will have well-measured peak absolute magnitudes encompassing the UV, optical, and near-infrared (NIR). Analysis of these observations will show whether the physical cause of the UV dispersion already observed in the UV peak magnitudes and colors also has an impact on the optical luminosities, thereby affecting the usefulness of SNe Ia as standard candles. The sensitivity of the UV to many of the systematic uncertainties (metallicity, extinction, viewing angle, etc) may allow the identification and correction of differences between otherwise “standard” candles. This program capitalizes on Swift’s unique strengths of rapid response, short term scheduling, and UV capabilities to improve our understanding of the standard candles essential to studies of the expanding universe.