The short-duration GRB 050724 host galaxy in the context of the long-duration GRB hosts

Free access article

Issue		A&A Volume 450, Number 1, April IV 2006


Page(s)		87 - 92
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20054373

A&A 450, 87-92 (2006)
DOI: 10.1051/0004-6361:20054373

The short-duration GRB 050724 host galaxy in the context of the long-duration GRB hosts

J. Gorosabel¹, A. J. Castro-Tirado¹, S. Guziy¹, A. de Ugarte Postigo¹, D. Reverte¹, A. Antonelli², S. Covino³, D. Malesani⁴, D. Martín-Gordón¹, A. Melandri², M. Jelínek¹, N. Elias de la Rosa⁵, O. Bogdanov⁶ and J. M. Castro Cerón⁷

¹ Instituto de Astrofísica de Andalucía (IAA - CSIC), Apartado de Correos, 3.004, 18.080 Granada, Spain
e-mail: jgu@iaa.es
² INAF - Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monteporzio Catone (Rome), Italy
³ INAF - Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy
⁴ International School for Advanced Studies (SISSA - ISAS), via Beirut 2-4, 34014 Trieste, Italy
⁵ INAF - Osservatorio Astronomico di Padova, via dell'Osservatorio 8, 36012 Asiago (VI), Italy
⁶ Astronomical Observatory of Nikolaev State University, Nikolskaja, 24, Nikolaev, 54030, Ukraine
⁷ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark

(Received 18 October 2005 / Accepted 13 December 2005)

Abstract
We report optical and near-infrared broad band observations of the short-duration GRB 050724 host galaxy, used to construct its spectral energy distribution (SED). Unlike the hosts of long-duration gamma-ray bursts (GRBs), which show younger stellar populations, the SED of the GRB 050724 host galaxy is optimally fitted with a synthetic elliptical galaxy template based on an evolved stellar population (age ~2.6 Gyr). The SED of the host is difficult to reproduce with non-evolving metallicity templates. In contrast, if the short GRB host galaxy metallicity enrichment is considered, the synthetic templates fit the observed SED satisfactorily. The internal host extinction is low ( $A_{\rm v} \lesssim 0.4$ mag) so it cannot explain the faintness of the afterglow. This short GRB host galaxy is more massive ( ${\sim}5\times10^{10}\, M_{\odot}$ ) and luminous ( ${\sim}1.1~ L^{\star}$ ) than most of the long-duration GRB hosts. A statistical comparison based on the ages of short- and long-duration GRB host galaxies strongly suggests that short-duration GRB hosts contain, on average, older progenitors. These findings support a different origin for short- and long-duration GRBs.

Key words: gamma rays: bursts -- Galaxy: fundamental parameters -- techniques: photometric

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