Type Ia Supernovae in the Ultraviolet, Optical, and Near-Infrared

Abstract

We present an ultraviolet (UV) spectroscopic atlas containing 91 spectra of 22 unique Type Ia supernovae (SNe Ia). The spectra were observed using the Ultraviolet/Optical Telescope (UVOT) onboard the Swift space telescope. We present a new technique of decontaminating UVOT grism spectra, which we apply to 40 of the spectra in our sample. We present the first UV spectroscopic series of a peculiar 1999aa-like SN Ia, iPTF14bdn, and compare to normal SNe in our sample. We find this SN to be very blue at early times due to a bright feature between 2800 - 3200Å. We attribute this to a lower UV opacity caused by higher temperatures above the SN photosphere, likely due to a greater quantity of ^56Ni in this region. We also identify the spectroscopic feature differences between 2700 - 3300Å responsible for the near-UV (NUV) photometric diversity. Comparison of these features to model data suggest that NUV-bluer SNe result from lower metal abundances in the outer ejecta layers.

We combine our UV spectral atlas with UV, optical and NIR photometry, and spectra to generate a UV-O-IR spectral series atlas for 8 SNe Ia near peak brightness. The UV-O-IR SEDs represent time evolution within -10 to +30 days of peak brightness, decline rates between 0.9 < Δm15(B) < 1.8, and UV subclassification (when known). Using these data, we calculate integrated bolometric luminosities and synthesized ^56Ni masses. We demonstrate that our UV-O-IR SEDs provide an improved method of calculating K-corrections for B-band optical photometry, and present an analysis of SNe Ia UV K-corrections. We present a method of calculating bolometric corrections which take the SNe decline rates into account for SNe near peak brightness.