Master Thesis Defense by Shu Yan Zheng
Title: An extensive analysis of the optical and near-infrared afterglow of the exceptionally bright gamma-ray burst of October 9 2022
Abstract: Gamma-ray bursts (GRBs) are the most luminous events known. They are furthermore powerful tools to study detailed properties of their host galaxies. In this project, the properties of the host galaxy for the brightest GRB observed to date, GRB221009A, are studied. To do so, spectroscopy is used based on data from the X-shooter instrument on the Very Large Telescope (VLT) as well as from instruments on the the James Webb Space Telescope. The spectra shows both absorption (atomic and diffuse interstellar bands) and emission lines from material in the host galaxy and in the Milky Way. The host galaxy is found to have a redshift of z = 0.1510214 ± 0.51 · 10−5 which yields a distance of d = 644.5 Mpc. The star formation rate is found to be SFR = 0.2024 ± 0.0097 M⊙/yr (statistical error). Furthermore, extinction functions were fitted to the continuum. The best fit is the model from E. L. Fitzpatrick and Massa 2007whichgivesatotalextinctionofAV =4.582±0.061frombothdustinthe MW and host galaxy and AV,host = 0.405 ± 0.256 from dust in the host galaxy alone. The properties of the afterglow and of the host galaxy are similar to those of other long GRBs. The only unusual or rare property of the event (other than the extreme brightness of the prompt emission) is the presence of absorption lines from exited Hydrogen and Helium.
Supervisor:
- Johan Peter Uldall Fynbo, University of Copenhagen, Niels Bohr Institute
Censor:
- Frank Grundahl, Aarhus University