GRB 050904 at redshift 6.3: observations of the oldest cosmic explosion after the Big Bang

TAGLIAFERRI, G.; ANTONELLI, L. A.; CHINCARINI, G.; FERNÁNDEZ-SOTO, A.; MALESANI, D.; DELLA VALLE, M.; D'AVANZO, P.; GRAZIAN, A.; TESTA, V.; CAMPANA, S.; COVINO, S.; FIORE, F.; STELLA, L.; CASTRO-TIRADO, A. J.; GOROSABEL, J.; BURROWS, D. N.; CAPALBI, M.; CUSUMANO, G.; CONCIATORE, M. L.; D'ELIA, V.; FILLIATRE, P.; FUGAZZA, D.; GEHRELS, N.; GOLDONI, P.; GUETTA, D.; GUZIY, S.; HELD, E. V.; HURLEY, K.; ISRAEL, G. L.; JELÍNEK, M.; LAZZATI, D.; LÓPEZ-ECHARRI, A.; MELANDRI, A.; MIRABEL, I. F.; MOLES, M.; MORETTI, A.; MASON, K. O.; NOUSEK, J.; OSBORNE, J.; PELLIZZA, L. J.; PERNA, R.; PIRANOMONTE, S.; PIRO, L.; DE UGARTE POSTIGO, A.; ROMANO, P.

ASTRONOMY AND ASTROPHYSICS

EDP Sciences

Lugar: Les Ulis; Año: 2005 vol. 443 p. 1 - 5

0004-6361

We present optical and near-infrared observations of the afterglow of the gamma-ray burst GRB 050904. We derive a photometric redshift z = 6.3, estimated from the presence of the Lyman break falling between the I and J filters. This is by far the most distant GRB known to date. Its isotropic-equivalent energy is 3.4 × 1053 erg in the rest-frame 110-1100 keV energy band. Despite the high redshift, both the prompt and the afterglow emission are not peculiar with respect to other GRBs. We find a break in the J-band light curve at tb = 2.6 ± 1.0 d (observer frame). If we assume this is the jet break, we derive a beaming-corrected energy E_㠘 (4 div 12) × 1051 erg. This limit shows that GRB 050904 is consistent with the Amati and Ghirlanda relations. This detection is consistent with the expected number of GRBs at z > 6 and shows that GRBs are a powerful tool to study the star formation history up to very high redshift.