Date of Award
Doctor of Philosophy (PhD)
Hartmann , Dieter
King , Jeremy
Oberheide , Jens
Type Ia supernovae (SNe Ia), the thermonuclear explosion of a white dwarf, shape our understanding of the expansion of the universe with the use of their uniformity in distance determinations. Powered by radioactivity synthesized in the explosion, they fade slowly over hundreds of days. Sometime after 200 days, the continually expanding ejecta allows γ-rays from 56 Ni and 56 Co decays to escape, and soon any radioactive power contributing to lighting up the SN comes from positrons formed in 19% of 56 Co
While at first it seemed that positrons escaped through the thinning ejecta, it has become apparent that conclusions can only be drawn from accounting for all the power from the near-infrared (NIR) as well as the optical. Only a handfull of SNe have been observed during epochs at a year after explosion in both the optical and NIR. These seem to make an argument for the complete trapping of positrons while also suggesting there is more power unobserved in other bands.
This dissertation discusses observations of three nearby SNe; 2006E, 2006ce, and 2006mq, which were all discovered after maximum light, but bright enough to be observed to late times (the latest at ∼525 days after peak). The late multi-wavelength observations are converted to fluxes and luminosity and we assess the behvaior of different wavelength regimes. A simple positron deposition model is employed to estimate the feasibility of positron escape. We find that we cannot rule out positron escape, but that it seems likely that there is a color evolution that shifts power away from observed bands. This shifting of power seems to vary from SN to SN and is not uniform across all normal SNe Ia.
Bryngelson, Ginger, "THE POWER OF THERMONUCLEAR SUPERNOVAE AFTER ONE YEAR" (2012). All Dissertations. 998.