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ID 46883
file
creator
Tashiro, Makoto S.
Onda, Kaori
Yamaoka, Kazutaka
Ohno, Masahiro
Sugita, Satoshi
Uehara, Takeshi
Seta, Hiromi
subject
gamma rays: burst
gamma rays: observation
radiation mechanisms: thermal
blackbody radiation; non-thermal
inverse Compton scattering
NDC
Astronomy. Space sciences
abstract
This paper presents a study on the spectral evolution of gamma-ray burst (GRB) prompt emissions observed with the Suzaku Wide-band All-sky Monitor (WAM). By making use of the WAM data archive, 6 bright GRBs exhibiting 7 well-separated fast-rise-exponential-decay (FRED) shaped light curves are presented, and the evaluated exponential decay time constants of the energy-resolved light curves from these FRED peak light curves are shown to indicate significant spectral evolution. The energy dependence of the time constants is well described with a power-law function, τ(⁠E⁠) ∝Eγ⁠, where γ∼−(0.34±0.12) on average, although 5 FRED peaks show a consistent value of γ=−1/2, which is expected in synchrotron or inverse-Compton cooling models. In particular, 2 of the GRBs were located with accuracy sufficient to evaluate the time-resolved spectra with precise energy response matrices. Their behavior in spectral evolution suggests two different origins of emissions. In the case of GRB 081224, the derived 1-s time-resolved spectra are well described by a blackbody radiation model with a power-law component. The derived behavior of cooling is consistent with that expected from radiative cooling or expansion of the emission region. On the other hand, the other 1-s time-resolved spectra from GRB 100707A is well described by a Band GRB model as well as with the thermal model. Although relative poor statistics prevent us to conclude, the energy dependence in the decaying light curve is consistent with that expected in the former emission mechanism model.
description
Part of this work was financially supported by the Ministry of Education, Culture, Sports, Science and Technology, Grant-in-Aid for Scientific Research No. 22340039.
journal title
Publications of the Astronomical Society of Japan
volume
Volume 64
issue
Issue 2
start page
26-1
end page
26-10
date of issued
2012-04-25
publisher
Astronomical Society of Japan
issn
0004-6264
ncid
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
author
rights
(c) 2012. Astronomical Society of Japan.
This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
relation url
department
Graduate School of Science