Emery, Samuel W. K.;
(2024)
A study of thermal components in gamma-ray burst afterglows.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The thesis presents a comprehensive analysis of thermal components observed in the afterglows of gamma-ray bursts (GRBs) via multi-wavelength obser vations. The primary objective is to unravel the mechanisms and charac teristics that shape the early afterglow emission phases. The study predomi nantly focuses on three specific GRB events: GRB 100316D, GRB 060218, and GW170817. For GRB 100316D, it was determined that UV/optical/X-ray emissions within 33-52 ks intervals indicate a blackbody component, poten tially suggesting a cooling envelope post-shock-breakout. A similar thermal emission pattern observed in GRB 060218 hints at potential commonalities in their underlying processes. Upon re-examination of GRB 060218, a syn chrotron component in the initial 1350s of the UV/optical spectra was iden tified, indicating a low-luminosity jet interaction after a core collapse. This phase is succeeded by dominant thermal radiation, with spectral data between 1350-10,000s aligning most accurately with a spherically outflowing blackbody model and an additional power-law component at X-ray wavelengths. In the case of GW170817, the simultaneous detection of a short gamma-ray burst coupled with a gravitational wave from a binary neutron star merger solidified the prevailing theory that such mergers can be precursors to short gamma-ray bursts. It was observed that immediate UV emissions, followed by UV/optical thermal emissions, support the hypothesis of an r-process event post-merger. Additionally, the thesis explores the influence of redshift on the detectability of thermal components in GRBs associated with supernovae. Higher redshift GRBs tend to show thermal detection in the XRT spectrum, possibly a result of cosmological dimming. The potential universality of thermal components in GRBs, occasionally overshadowed by the afterglow’s luminosity, underscores the importance of multi-wavelength observations. The research endeavours to deepen the understanding of the origins, intricate characteristics, and wider ramifications of thermal emissions in GRBs.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | A study of thermal components in gamma-ray burst afterglows |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10191363 |
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