Optical emission from GRB 050709: a short/hard GRB in a star forming galaxy

S. Covino; D. Malesani; G. L. Israel; P. D'Avanzo; L. A. Antonelli; G. Chincarini; D. Fugazza; M. L. Conciatore; M. Della Valle; F. Fiore; D. Guetta; K. Hurley; D. Lazzati; L. Stella; G. Tagliaferri; M. Vietri; S. Campana; D. N. Burrows; V. D'Elia; P. Filliatre; N. Gehrels; P. Goldoni; A. Melandri; S. Mereghetti; I. F. Mirabel; A. Moretti; J. A. Nousek; P. T. O'Brien; L. J. Pellizza; R. Perna; S. Piranomonte; P. Romano; F. M. Zerbi

doi:10.1051/0004-6361:200500228

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Optical emission from GRB 050709: a short/hard GRB in a star forming galaxy

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Abstract

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 z = 0.1606 +- 0.0002. 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 2-3 (L/L*) Msun/yr. 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.

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S. Covino, D. Malesani, G. L. Israel, P. D'Avanzo, L. A. Antonelli, G. Chincarini, D. Fugazza, M. L. Conciatore, M. Della Valle, F. Fiore, D. Guetta, K. Hurley, D. Lazzati, L. Stella, G. Tagliaferri, M. Vietri, S. Campana, D. N. Burrows, V. D'Elia, P. Filliatre, N. Gehrels, P. Goldoni, A. Melandri, S. Mereghetti, I. F. Mirabel, A. Moretti, J. A. Nousek, P. T. O'Brien, L. J. Pellizza, R. Perna, S. Piranomonte, P. Romano, F. M. Zerbi. 2006-01-10. Optical emission from GRB 050709: a short/hard GRB in a star forming galaxy. https://doi.org/10.1051/0004-6361%3A200500228

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