Letter to the Editor

A photometric redshift of z = 1.8 for the AGILE GRB 080514B^*

¹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany e-mail: rossi@tls-tautenburg.de
² European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19, Chile
³ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
⁴ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
⁵ Darthmouth College, Hanover, NH 03755, USA
⁶ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
⁷ Universe Cluster, Technische Universität München, Boltzmannstraße 2, 85748, Garching, Germany
⁸ Institute of Physics, Eötvös University, Pázmány P. s. 1/A, 1117 Budapest, Hungary
⁹ Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
¹⁰ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
¹¹ Instituto de Astrofísica de Andalucía (IAA-CSIC), Apartado de Correos 3.004, 18080 Granada, Spain
¹² Universidad de Valencia, Edif. Institutos de Investigación (GACE-ICMOL), Campus de Paterna, 46980 Paterna, Spain
¹³ Clemson University, Department of Physics and Astronomy, Clemson, SC 29634-0978, USA
¹⁴ INAF/IASF - Milano, via E. Bassini 15, 20133 Milano, Italy
¹⁵ Astrophysics Science Division, Code 660.1, 8800 Greenbelt Road, Goddard Space Flight Centre, Greenbelt, MD 20771, USA
¹⁶ School of Physics, University College Dublin, Dublin 4, Ireland
¹⁷ Institut de Radio Astronomie Millimetrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin d'Hères, France
¹⁸ Instituto de Astrofísica de Canarias (IAC), C/. via Láctea s/n, 38205 La Laguna (Tenerife), Spain

Received: 1 August 2008
Accepted: 6 October 2008

Abstract

The AGILE gamma-ray burst GRB 080514B is the first detected to have emission above 30 MeV and an optical afterglow. However, no spectroscopic redshift for this burst is known. We report on our ground-based optical/NIR and millimeter follow-up observations of this event at several observatories, including the multi-channel imager GROND on La Silla, supplemented by Swift UVOT and Swift XRT data. The spectral energy distribution (SED) of the optical/NIR afterglow is found to decline sharply bluewards to the UV bands, which can be utilized in estimating the redshift. Fitting the SED from the Swift UVOT band to the H band, we estimate a photometric redshift of , which is consistent with the reported pseudo-redshift based on gamma-ray data. We find that the afterglow properties of GRB 080514B do not differ from those exhibited by the global sample of long bursts. Compared with the long burst sample, we conclude that this burst was special because of its high-energy emission properties, even though both its afterglow and host galaxy are not remarkable in any way. Obviously, high-energy emission in the gamma-ray band does not automatically correlate with the occurrence of special features in the corresponding afterglow light.