Gamma-Ray Burst observations by the Square Kilometre Array. New perspectives
Creators: name: Ruggeri, Alan Cosimo
Publisher: name: Università degli Studi di Napoli Federico II
Year: 2015

description: Gamma-Ray Bursts (GRBs) are the most powerful astrophysical source in the universe and have been studied since the '70s. Nevertheless, these objects are still not completely understood and many hypotheses have not been confirmed yet. Past and current observations have been made mostly at gamma, X and optical frequencies. This thesis aims to promote radio GRB observations, in order to thin out a menagerie of different opinions about these sources. In fact, GRBs have been prevalently studied as single cases, more often highlighting their peculiar features than elucidating their common characteristics, and thus leading to fragment the problem. Here the general properties are discussed, so that the attention is moved from the exception to the general case. In other words, this work suggests viewing GRBs in a broad ensemble instead of searching out single cases to explain every peculiarity and as a result increasing the number of possible groups to categorize them. \par This work concerns astrophysics, Gamma-Ray Bursts (GRBs) sources, the \textit{Square Kilometre Array} (SKA) radio telescope, radio observations and cosmology. For this reason, it has been divided into three parts, with six chapters in total. Each chapter is a step that leads to the next one following a precise scheme. In the end, all this work highlights both the importance of GRB radio observations and their real feasibility. \\ The first part concerns the high energies and consists of two chapters. The first chapter contains an overview about GRB state of the art, showing how from the gamma range the GRB afterglow emission reaches the lower frequency range up to the radio band. The second chapter passes from the theory to the practice, where different GRB satellite missions are listed with their gamma payloads, having thus an idea about GRB detection. \par The second part is dedicated solely to the radio observations. Chapter 3 regards radio instrumentations and so the SKA is introduced here. This chapter may need some elucidation. My Ph.D. has been carried out between the University and the \textit{Societa' Aerospaziale Mediterranea S.c.r.l.} company, hence on one hand I have been able to conduct a study about GRBs, on the other hand I have had the opportunity to collaborate with a company in charge of designing the feed indexer of the SKA. This mechanical component will be assembled with the telescope antenna to select the receivers during the radio observations and details are contained in the chapter. \\ Since the SKA is a interferometer, chapter 4 regards the radio interferometry. This brief introduction to interferometry helps for the reading of the next chapter, where GRB radio observations are discussed. Chapter 5 concerns principally three works in radio astronomy. Firstly, the first radio observations ever for a very large GRB sample are presented. Secondly, the first considerations deduced from analyses of those first results. Finally, a work of mine currently submitted to the \textit{Monthly Notices of the Royal Astronomical Society} where it is discussed the GRB detection rate for the SKA. \par After discussions of observational techniques, detections and possible observational studies in the radio band about GRBs, the third part and its last chapter close the thesis by explaining what advantages a precise and complete study of GRBs can provide for cosmology. Indeed, these sources will be able to shine a light on the various cosmological models created to attempt to explain the expansion of the universe. This last point will be possible only when GRBs are studied proceeding with the precise method suggested here, considering GRBs as complex sources which must be observed and analyzed at all available wavelengths.