Identification and investigations of untriggered magnetar bursts in the fermi gamma-ray burst monitor database

Official URL: https://risc01.sabanciuniv.edu/record=b2767353_(table of contenst)

Magnetars are isolated neutron stars with extremely high magnetic fields that are known to emit short bursts. In this thesis, short bursts from two magnetars, Swift J1818.0-1607 and PSR J1846.4-0258 (a rotation-powered pulsar), which were burst active during 2020 and early 2021 were investigated, using Fermi Gamma-ray Burst Monitor (GBM) data. Firstly, candidate events were identified among the blind search results with GBM data, based on positive correlation between the count rates and cosine of the angles between the detectors’ zenith to a specific source. Then, we filtered events with non-positive correlation out of our event sample by considering that they were not originated from Swift J1818.0-1607 or PSR J1846.4-0258. We identified 115 bursts likely coming from these sources in total. Moreover, we performed spectral analysis for all spectra in 8-200 keV energy range and at 8 ms resolution using Comptonized (COMPT), single black body (BB), and sum of two black body models (BB+BB). We found that the identified bursts in our sample have relatively shorter duration in comparison to the other magnetar bursts in literature. Moreover, these bursts can be modeled well by BB. For both sources, we found similar BB temperatures as kT ≥ 10≠11 keV. Also, we found that there is a negative correlation between kT and the emission area as reported in other magnetar studies.