Application and analysis of the induced gravitational collapse in some gamma-ray bursts - supernovae

The title of the thesis is related to a larger study by a scientific group which I have been part of during the PhD course. The study of the group is related to developing Fireshell model in order to explain gamma-ray bursts; Induced Gravitational Collapse model in order to explain their connection to supernovae; and interpreting individual gamma-ray bursts, and groups of them, within these models. The thesis is a compilation of various work done by me during the duration of the PhD course related to the topic stated in the title. Not everything done during the PhD is presented in the thesis mainly due to time limitations. One of the non-included work consists of analysis of high-energy data from numerous gamma-ray bursts obtained by Fermi-LAT and Fermi-GBM space-based detectors, automating such analysis, looking for peculiarities and trying to find patterns in it, and trying to determine weather such features are intrinsic or due to instrumental effects. The thesis is structured as follows: In Chapter 1 history of Gamma-ray burst discoveries and general conclusions which came from them will be presented. In Chapter 2 general information will be presented on the Fireball model, which is a mainstream model used to explain gamma-ray bursts. Then the general information on the Fireshell model will be presented. This will take a form of a short review of the work done by the group on the topic. In Chapter 3 the general information on the Induced Gravitational Collapse model will be presented. Again this will be a short review of the work done by the group. Since late 2013, I contributed in part to some of the analysis of high energy data and to lesser extent on statistics of gamma-ray burst observational properties. In Chapter 4, I will present my work which started with systematic analysis of Swift- BAT and Swift-XRT data with the aims of detecting thermal black body emission in the late prompt phase of gamma-ray bursts. This involved close examination of data analysis techniques and writing Python scripts in order to automatize data analysis as much as possible. Then the results of several detected black bodies will be compared to each other in the rest-frame of gamma-ray burst host galaxy. Afterward the corrections due to relativistic expansion of the black body will be derived. Next a small simulation of spectrum from a black body with mildly relativistic expansion, and with varying velocity and temperature, will be done and the simulation applied to GRB 151027A. Finally the results will be compared to predictions of Induced Gravitational Collapse model. It was found that they are not in contradiction with the model. In Chapter 5 the work which involved cross-correlation of gamma-ray burst and supernova catalogs in order to find potentially unnoticed connections up to mid 2014 will be presented. One probable such connection was found between Ic supernova and low luminosity gamma-ray burst, and the rate of such events were calculated. It was found they overlap with previous estimates. I was one of the people leading the work. Next I will update the work with the same analysis up to year 2017 applying different statistical methods and involving more catalogs. The novel results indicate possible connection between short gamma-ray bursts and type IIn supernovae. The investigation of such possibility will be carried out and its implications will be examined.