Issue |
A&A
Volume 483, Number 3, June I 2008
|
|
---|---|---|
Page(s) | 847 - 855 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20078677 | |
Published online | 11 March 2008 |
Early emission of rising optical afterglows: the case of GRB 060904B and GRB 070420 *
1
Observatoire de Haute-Provence, 04870 Saint Michel l'Observatoire, France
2
CESR, Observatoire Midi-Pyrénées, CNRS, Université de Toulouse, BP 4346, 31028 Toulouse Cedex 04, France e-mail: klotz@cesr.fr
3
Istituto di Astrofisica Spaziale e Fisica Cosmica, Sede di Roma, INAF, via Fosso del Cavaliere 100, 00133 Roma, Italy
4
University degli Studi di Milano–Bicocca, Piazza dell'Ateneo Nuovo, 20126, Milano, Italy
5
ASI Science Data Center (ASDC), via G. Galilei, 00044 Frascati, Italy (INAF personnel resident at ASDC under ASI contract 1/024/05/0.)
6
INFN-Trieste, Padriciano 99, 34012 Trieste, Italy
7
Università di Perugia, Dipartimento di fisica, viale A. Pascoli, 06123 Perugia, Italy
8
LATT, Observatoire Midi-Pyrénées, CNRS, Université de Toulouse, 14 avenue E. Belin, 31400 Toulouse, France
Received:
14
September
2007
Accepted:
8
February
2008
Aims. We present the time-resolved optical emission of gamma-ray bursts GRB 060904B and GRB 070420 during their prompt and early afterglow phases.
Methods. We used time resolved photometry from optical data taken by the TAROT telescope and time resolved spectroscopy at high energies from the Swift spacecraft instrument.
Results. The optical emissions of both GRBs are found to increase from the end of the prompt phase,
passing to a maximum of brightness at min and 3.3 min for
GRB 060904B and GRB 070420 respectively and then decrease.
GRB 060904B presents a large optical plateau and a very large X-ray flare.
We argue that the very large X-flare occurring near tpeak is produced
by an extended internal engine activity and is only
a coincidence with the optical emission. GRB 070420 observations would support
this idea because there was no X-flare during the optical peak. The nature
of the optical plateau of GRB 060904B is less clear and might be related to the
late energy injection.
Key words: gamma ray : bursts
© ESO, 2008
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.