Ending the prompt phase in photospheric models of gamma-ray bursts
2024 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 683, article id A30Article in journal (Refereed) Published
Abstract [en]
The early steep decay, a rapid decrease in X-ray flux as a function of time following the prompt emission, is a robust feature seen in almost all gamma-ray bursts with early enough X-ray observations. This peculiar phenomenon has often been explained as emission from high latitudes of the last flashing shell. However, in photospheric models of gamma-ray bursts, the timescale of high-latitude emission is generally short compared to the duration of the steep decay phase, and hence an alternative explanation is needed. In this paper we show that the early steep decay can directly result from the final activity of the dying central engine. We find that the corresponding photospheric emission can reproduce both the temporal and spectral evolution observed. This requires a late-time behaviour that should be common to all gamma-ray burst central engines, and we estimate the necessary evolution of the kinetic power and the Lorentz factor. If this interpretation is correct, observation of the early steep decay can give us insights into the last stages of central activity, and provide new constraints on the late evolution of the Lorentz factor and photospheric radius.
Place, publisher, year, edition, pages
EDP Sciences , 2024. Vol. 683, article id A30
Keywords [en]
gamma-ray burst: general, radiation mechanisms: general, X-rays: general
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:kth:diva-344335DOI: 10.1051/0004-6361/202348310ISI: 001178890200004Scopus ID: 2-s2.0-85186612607OAI: oai:DiVA.org:kth-344335DiVA, id: diva2:1844338
Note
QC 20240314
2024-03-132024-03-132024-04-29Bibliographically approved