Speaker
Description
GRB 221009A stood out as the brightest GRB detected to date, offering a remarkable opportunity to delve into the intricacies of GRB physics. In this work, we investigated the prompt emission and afterglow characteristics of this unique burst utilizing observations from several missions like Swift, Fermi, and INTEGRAL including our early photometric (prior prompt emission) and spectroscopic observations taken using various telescopes. High-energy results show an ultra-long GRB (ULGRB) nature, with a prompt emission duration exceeding 1000 s. We examined its origin (through observations and simulation in MESA) and central engine and compared it with a nearly complete sample (categorizing the sample to Bronze, Silver, and Gold based on T90 duration) of Swift-detected GRBs with measured redshifts. Notably, the Gold sub-sample (a higher likelihood of being ULGRB candidates, including the "BOAT") suggests a collapsar scenario with a hyper-accreting black hole as a potential central engine. Our early optical observations during the prompt emission of GRB 221009A help to discard the presence of any bright optical emission with internal or external origin. We determine the distance to GRB 221009A through spectroscopy (taken with 10.4m GTC) of absorption and emission lines and establish the burst to be associated with a star-forming galaxy. Additionally, we conducted a comparative analysis of the properties of host galaxies associated with TeV-detected bursts including the BOAT, to acquire insights into the environments of TeV GRBs.
