Letter to the Editor
INAF-Astronomical Observatory of Rome, via Frascati 33, 00040 Monteporzio (Rome), Italy e-mail: firstname.lastname@example.org
2 INAF-Astronomical Observatory of Brera, via E. Bianchi 46, Merate (LC) 23807, Italy
3 Università degli Studi di Milano “Bicocca”, Piazza delle Scienze 3, 20126 Milano, Italy
4 JILA, Campus Box 440, University of Colorado, Boulder, CO 80309-0440, USA
5 INAF D Istituto di Astrofisica Spaziale e Fisica Cosmica, via Gobetti 101, 40126 Bologna, Italy
6 ASI Science Data Center, Via Galileo Galilei, 00044 Frascati (Roma), Italy
7 Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
8 Universitá degli Studi di Roma “Tor Vergata”, Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Roma, Italy
9 Laboratoire APC, Universitè Paris 7, 10 rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13, France
Accepted: 27 October 2009
Aims. With an observed and rest-frame duration of <2 s and <0.5 s, respectively, GRB 090426 could be classified as a short GRB. The prompt detection, both from space and ground-based telescopes, of a bright optical counterpart to this GRB offered a unique opportunity to complete a detailed study.
Methods. Based on an extensive ground-based observational campaign, we obtained the spectrum of the optical afterglow of GRB 090426, measuring its redshift and obtaining information about the medium in which the event took place. We completed follow-up observations of the afterglow optical light curve down to the brightness level of the host galaxy that we firmly identified and studied. We also retrieved and analyzed all the available high-energy data of this event, and compared the results with our findings in the optical. This represents one of the most detailed studies of a short-duration event presented so far.
Results. The time properties qualify GRB 090426 as a short burst. In this case, its redshift of would be the highest yet found for a GRB of this class. On the other hand, the spectral and energy properties are more similar to those of long bursts. LBT late-time deep imaging identifies a star-forming galaxy at a redshift consistent with that of the GRB. The afterglow lies within the light of its host and shows evidence of local absorption.
Key words: gamma ray: bursts
© ESO, 2009