Issue |
A&A
Volume 447, Number 2, February IV 2006
|
|
---|---|---|
Page(s) | L5 - L8 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:200500228 | |
Published online | 07 February 2006 |
Letter to the Editor
Optical emission from GRB 050709: a short/hard GRB in a star-forming galaxy
1
INAF, Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy e-mail: covino@mi.astro.it
2
International School for Advanced Studies (SISSA-ISAS), via Beirut 2-4, 34014 Trieste, Italy
3
INAF, Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monteporzio Catone (Roma), Italy
4
Dipartimento di Fisica e Matematica, Università dell'Insubria, via Valleggio 11, 22100 Como, Italy
5
Università degli studi di Milano-Bicocca, Dipartimento di Fisica, piazza delle Scienze 3, 20126 Milano, Italy
6
INAF, Osservatorio Astrofisico di Arcetri, largo E. Fermi 5, 50125 Firenze, Italy
7
University of California, Berkeley, Space Sciences Laboratory, Berkeley, CA 94720-7450, USA
8
JILA, University of Colorado, 440 UCB, Boulder CO 80309-0440, USA
9
Scuola Normale Superiore, piazza dei Cavalieri 7, 56126 Pisa, Italy
10
Department of Astronomy & Astrophysics, Pennsylvania State University, State College, PA 16801, USA
11
Laboratoire Astroparticule et Cosmologie, UMR 7164, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France
12
Service d'Astrophysique, DSM/DAPNA, CEA Saclay, 91911 Gif-sur-Yvette Cedex, France
13
NASA, Goddard Space Flight Center, Greenbelt, MD 20771, USA
14
Università degli Studi di Cagliari, Dipartimento di Fisica, 09042 Monserrato (Ca), Italy
15
INAF/IASF Milano “G. Occhialini”, via E. Bassini 15, 20133 Milano, Italy
16
European Southern Observatory - Vitacura, Casilla 19001, Santiago 19, Chile
17
X-Ray & Observational Astronomy Group, Dept. of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK
Received:
7
September
2005
Accepted:
21
December
2005
We present optical observations of the short/hard gamma-ray burst
GRB 050709, the first such event with an identified optical
counterpart. The object is coincident with a weak X-ray source and is
located inside a galaxy at redshift . Multiband
photometry allowed us to study the broad-band spectral energy
distribution.
Late-time monitoring places strong limits on any supernova simultaneous
with the GRB. The host galaxy is not of early type. Spectra show that
the dominant stellar population is relatively young (∼1 Gyr), and
that ongoing star formation is present at a level of
yr-1. This is at least 2 orders of magnitude
larger than that observed in the elliptical hosts of the short
GRB 050509B and GRB 050724. This shows that at least some short GRBs
originate in a young population. Short/hard GRB models based on the
merger of a binary degenerate system are compatible with the host galaxy
characteristics, although there is still the possibility of a connection
between young stars and at least a fraction of such events.
Key words: radiation mechanisms: non-thermal / gamma rays: bursts / gamma rays: individual GRB 050709
© ESO, 2006
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