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Testing a model for subphotospheric dissipation in GRBs: fits to Fermi data constrain the dissipation scenario
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.ORCID iD: 0000-0003-4000-8341
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.ORCID iD: 0000-0003-0065-2933
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.ORCID iD: 0000-0002-0642-1055
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2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, p. 474-497Article in journal (Refereed) Published
Abstract [en]

It has been suggested that the prompt emission in gamma-ray bursts (GRBs) could be described by radiation from the photosphere in a hot fireball. Such models must be tested by directly fitting them to data. In this work we use data from the Fermi Gamma-ray Space Telescope and consider a specific photospheric model, in which the kinetic energy of a low-magnetization outflow is dissipated locally by internal shocks below the photosphere. We construct a table model with a physically motivated parameter space and fit it to time-resolved spectra of the 36 brightest Fermi GRBs with a known redshift. We find that about two-thirds of the examined spectra cannot be described by the model, as it typically underpredicts the observed flux. However, since the sample is strongly biased towards bright GRBs, we argue that this fraction will be significantly lowered when considering the full population. From the successful fits we find that the model can reproduce the full range of spectral slopes present in the sample. For these cases we also find that the dissipation consistently occurs at a radius of ∼1012 cm and that only a few per cent efficiency is required. Furthermore, we find a positive correlation between the fireball luminosity and the Lorentz factor. Such a correlation has been previously reported by independent methods. We conclude that if GRB spectra are due to photospheric emission, the dissipation cannot only be the specific scenario we consider here.

Place, publisher, year, edition, pages
2019. Vol. 485, p. 474-497
Keywords [en]
gamma-ray burst
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-245227DOI: 10.1093/mnras/stz110ISI: 000466786400034OAI: oai:DiVA.org:kth-245227DiVA, id: diva2:1294485
Note

QC 20190308

Available from: 2019-03-07 Created: 2019-03-07 Last updated: 2019-05-29Bibliographically approved
In thesis
1. Investigating subphotospheric dissipation in gamma-ray bursts by fitting a physical model
Open this publication in new window or tab >>Investigating subphotospheric dissipation in gamma-ray bursts by fitting a physical model
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 76
Series
TRITA-SCI-FOU ; 2019:14
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-245241 (URN)978-91-7873-140-4 (ISBN)
Public defence
2019-03-29, FA31, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Supervisors
Note

QC 20190308

Available from: 2019-03-08 Created: 2019-03-07 Last updated: 2019-03-08Bibliographically approved

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Publisher's full texthttps://academic.oup.com/mnras/article-abstract/485/1/474/5301414?redirectedFrom=PDF

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Ahlgren, BjörnLarsson, JosefinAhlberg, ErikLundman, ChristofferRyde, Felix

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