Gamma-ray bursts with MeerLICHT
| dc.contributor.advisor | Groot, Paul Joseph | |
| dc.contributor.author | De Wet, Simon | |
| dc.date.accessioned | 2025-02-04T14:05:34Z | |
| dc.date.available | 2025-02-04T14:05:34Z | |
| dc.date.issued | 2024 | |
| dc.date.updated | 2025-02-04T14:03:17Z | |
| dc.description.abstract | The subject of this thesis is the multi-wavelength observational study of gamma-ray burst (GRB) afterglows. The driving force behind this work is the fully robotic MeerLICHT optical telescope which is able to rapidly slew to the position of a GRB in the sky and obtain multi-lter follow-up observations of the early phases of the afterglow, when non-standard behaviour may occur. Following the introduction, the thesis consists of four main chapters: a chapter outlining the more than two year GRB follow-up programme undertaken with MeerLICHT in which we followed-up 29 bursts, and three chapters presenting detailed studies on individual GRBs. The rst of these studies focuses on GRB 210731A. Starting 286 seconds post-trigger, MeerLICHT obtained a highly unusual light curve consisting of three peaks, which we interpreted as being due to energy injection. Through multi-wavelength theoretical modeling we found that a forward shock model within a stellar wind medium could explain all of our X-ray, optical and radio data, but not our 1.4 GHz upper limits. We suggested that a possible thermal electron population might explain the additional opacity at lower radio frequencies. The subject of the second detailed study is GRB 220627A, a rare burst consisting of two gamma-ray emission episodes separated by almost 1000 s. The discovery of the optical afterglow by MeerLICHT led to spectroscopic observations which secured the burst redshift to z=3.08, making this the most distant ultra-long GRB to date. Our modelling and afterglow analysis showed that GRB 220627A does not appear to have a dierent progenitor compared to the wider long GRB propulation. The third detailed study encompasses GRB 210702A. This burst was unique for being the rst GRB with a clear rebrightening in its millimeter light curve which we attempted to explain via energy injection or a reverse shock from a late-time shell collision. Prior to the millimeter rebrightening, we found that the X-ray, optical and millimeter data could be reconciled within a standard forward shock model in a stellar wind medium, however, similar to other bursts with extensive radio data sets, no standard model could explain all of our radio data. | |
| dc.identifier.apacitation | De Wet, S. (2024). <i>Gamma-ray bursts with MeerLICHT</i>. (). University of Cape Town ,Faculty of Science ,Department of Astronomy. Retrieved from http://hdl.handle.net/11427/40880 | en_ZA |
| dc.identifier.chicagocitation | De Wet, Simon. <i>"Gamma-ray bursts with MeerLICHT."</i> ., University of Cape Town ,Faculty of Science ,Department of Astronomy, 2024. http://hdl.handle.net/11427/40880 | en_ZA |
| dc.identifier.citation | De Wet, S. 2024. Gamma-ray bursts with MeerLICHT. . University of Cape Town ,Faculty of Science ,Department of Astronomy. http://hdl.handle.net/11427/40880 | en_ZA |
| dc.identifier.ris | TY - Thesis / Dissertation AU - De Wet, Simon AB - The subject of this thesis is the multi-wavelength observational study of gamma-ray burst (GRB) afterglows. The driving force behind this work is the fully robotic MeerLICHT optical telescope which is able to rapidly slew to the position of a GRB in the sky and obtain multi-lter follow-up observations of the early phases of the afterglow, when non-standard behaviour may occur. Following the introduction, the thesis consists of four main chapters: a chapter outlining the more than two year GRB follow-up programme undertaken with MeerLICHT in which we followed-up 29 bursts, and three chapters presenting detailed studies on individual GRBs. The rst of these studies focuses on GRB 210731A. Starting 286 seconds post-trigger, MeerLICHT obtained a highly unusual light curve consisting of three peaks, which we interpreted as being due to energy injection. Through multi-wavelength theoretical modeling we found that a forward shock model within a stellar wind medium could explain all of our X-ray, optical and radio data, but not our 1.4 GHz upper limits. We suggested that a possible thermal electron population might explain the additional opacity at lower radio frequencies. The subject of the second detailed study is GRB 220627A, a rare burst consisting of two gamma-ray emission episodes separated by almost 1000 s. The discovery of the optical afterglow by MeerLICHT led to spectroscopic observations which secured the burst redshift to z=3.08, making this the most distant ultra-long GRB to date. Our modelling and afterglow analysis showed that GRB 220627A does not appear to have a dierent progenitor compared to the wider long GRB propulation. The third detailed study encompasses GRB 210702A. This burst was unique for being the rst GRB with a clear rebrightening in its millimeter light curve which we attempted to explain via energy injection or a reverse shock from a late-time shell collision. Prior to the millimeter rebrightening, we found that the X-ray, optical and millimeter data could be reconciled within a standard forward shock model in a stellar wind medium, however, similar to other bursts with extensive radio data sets, no standard model could explain all of our radio data. DA - 2024 DB - OpenUCT DP - University of Cape Town KW - astronomy LK - https://open.uct.ac.za PB - University of Cape Town PY - 2024 T1 - Gamma-ray bursts with MeerLICHT TI - Gamma-ray bursts with MeerLICHT UR - http://hdl.handle.net/11427/40880 ER - | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11427/40880 | |
| dc.identifier.vancouvercitation | De Wet S. Gamma-ray bursts with MeerLICHT. []. University of Cape Town ,Faculty of Science ,Department of Astronomy, 2024 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/40880 | en_ZA |
| dc.language.rfc3066 | eng | |
| dc.publisher.department | Department of Astronomy | |
| dc.publisher.faculty | Faculty of Science | |
| dc.publisher.institution | University of Cape Town | |
| dc.subject | astronomy | |
| dc.title | Gamma-ray bursts with MeerLICHT | |
| dc.type | Thesis / Dissertation | |
| dc.type.qualificationlevel | Doctoral | |
| dc.type.qualificationlevel | PhD |