Investigation of short gamma-ray bursts with extended emission

Gamma-ray bursts (GRBs) are traditionally divided into two basic classes as short and long GRBs. The general idea about the formation of these bursts is that short bursts are caused by the merger of binary compact objects, while longs are caused by massive star's core collapse to form a black hole. With the increase in data from space missions dedicated for these bursts that occur on average several times a day, many observations that do not fit this theoretical framework have been recorded, so that the idea that these "outlier" GRBs may belong to the separate populations. One of the populations mentioned is "short GRBs with extended emission (EE)", which is a hybrid class that has the characteristics of both short and long bursts and is the focus of this thesis. Although the formation of GRBs with EE is usually explained with the protomagnetars or two-component jet model, it is essential to solidify their observational basis in order to test theories about this hybrid class and develop new ideas. In this context, certain criteria were applied to the light curves of all GRBs observed with the Swift/BAT detector between February 2013 and August 2020 in order to determine the explosions that should be examined in the short GRB with EE class. The relevant criteria are based on morphological similarity to the light curve of the GRB060614A burst, an obvious example of the hybrid class. As a result of the research, although 25 of the GRBs in the relevant time period were cataloged as long GRBs, it was determined that the light curve was suitable for the short GRB structure. Considering all short GRBs, it was determined that 17 of them had at least one EE component in the first 350 seconds. Detailed spectral analysis was performed for the prompt and EE components of the identified 17 EE GRBs and it was found that the component times were strongly correlated with the spectral hardness ratio, maximum energy flux, and spectral index. Correlation coefficients between some other important parameters are also presented within the framework of the thesis study, and it has also been shown that all Swift/BAT catalog member GRBs are suitable for the two-component jet model. Since the Swift/BAT catalog was searched with the same criteria in the literature before February 2013, this thesis study is complementary in terms of distinguishing short, long and short GRB with EE components for bursts in the entire Swift/BAT GRB catalog.