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P.A. Milne, M. D. Leising, L. S. The (Clemson University)
This dissertation investigates the contributions of supernovae (SNe) to galactic positrons. Previous works have suggested that for favorable conditions, 56Co positrons can escape from the SN ejecta into the ISM. The lifetimes of positrons are long enough to permit the contributions of many SNe to collectively produce a ``sea of positrons". The transport of positrons through SN ejecta and annihilation of positrons in the ISM give rise to two observable effects; the deposition of positron kinetic energy into the SN ejecta drives the SN emission at late times, and the annihilation of positrons with electrons in the ISM produces 511 keV photons. We model the transport of positrons in SN ejecta, estimating positron yields and generating bolometric light curves. The curves are compared with observed SN light curves and positron escape is indicated.
The yields from SN models are combined with SN rates, galactic SN distributions and estimates of the yield of positrons from other SN-synthesized positron emitting radionuclei to generate a collective SN map of the galactic annihilation radiation. The SN map and many other maps are then compared to the observations of galactic annihilation radiation taken by the Oriented Scintillation Spectrometer Experiment (OSSE) to determine if the SN map is favored. The SN distribution was found to agree with the data if certain assumptions are made about the distribution of type Ia SNe in the Galaxy, and if other sources of galactic annihilation radiation were present. We conclude with a discussion of what observations would further the arguments for positron escape from SNe, and the SN galactic annihilation radiation map.
The author(s) of this abstract have provided an email address for comments about the abstract: pmilne@clemson.edu