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Thermal components in the early X-ray afterglow of gamma-ray bursts
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Gamma-ray bursts (GRBs) are still puzzling scientists even 40 years after their discovery. Questions concerning the nature of the progenitors, the connection with supernovae and the origin of the high-energy emission are still lacking clear answers. Today, it is known that there are two populations of GRBs: short and long. It is also known that long GRBs are connected to supernovae (SNe). The emission observed from GRBs can be divided into two phases: the prompt emission and the afterglow. This thesis presents spectral analysis of the early X-ray afterglow of GRBs observed by the {\it Swift} satellite. For the majority of GRBs the early X-ray afterglows are well described by an absorbed power-law model. However, there exists a number of cases where this power-law component fails in fully describing the observed spectra and an additional blackbody component is needed. In the paper at the end of this thesis, a time-resolved spectral analysis of 74 GRBs observed by the X-ray telescope on board {\it Swift} is presented. Each spectrum is fitted with a power-law and a power-law plus blackbody model. The significance of the added thermal component is then assessed using Monte Carlo simulations. Six new cases of GRBs with thermal components in their spectra are presented, alongside three previously reported cases. The results show that a cocoon surrounding the jet is the most likely explanation for the thermal emission observed in the majority of GRBs. In addition, the observed narrow span in radii points to these GRBs being produced in similar environments.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , 50 p.
Series
TRITA-FYS, ISSN 0280-316X ; 2017:63
National Category
Astronomy, Astrophysics and Cosmology Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-217103ISBN: 978-91-7729-541-9 (print)OAI: oai:DiVA.org:kth-217103DiVA: diva2:1153673
Presentation
2017-10-27, FD5, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20171031

Available from: 2017-11-01 Created: 2017-10-31 Last updated: 2017-11-01Bibliographically approved
List of papers
1. Thermal components in the early X-ray afterglows of GRBs: likely cocoon emission and constraints on the progenitors
Open this publication in new window or tab >>Thermal components in the early X-ray afterglows of GRBs: likely cocoon emission and constraints on the progenitors
(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-217101 (URN)
Note

QC 20171031

Available from: 2017-10-31 Created: 2017-10-31 Last updated: 2017-10-31Bibliographically approved

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