EUROPEAN SPACE AGENCY

GRB 050223: a dark GRB in a dusty starburst galaxy

DOI: 10.1051/0004-6361:20066015 Bibcode: 2006A&A...459L...5P

Cimatti, A.; Le Floc'h, E.; Piro, L.; Covino, S.; Campana, S.; Della Valle, M.; Tagliaferri, G.; Antonelli, L. A.; Fugazza, D.; Chincarini, G.; Goldoni, P.; Stella, L.; Fiore, F.; Duc, P. -A.; Moretti, A.; Giommi, P.; Israel, G. L.; Mirabel, I. F.; Molinari, E.; Saracco, P.; Pellizza, L. J.; Vietri, M.

France, Argentina, United States, Italy

Abstract

Aims.We aim at detecting and determining the properties of the host galaxy of the dark GRB 050223.
Methods: .We use VLT optical/NIR images coupled to Swift X-ray positioning, and optical spectra of the host galaxy to measure its properties.
Results: .We find a single galaxy within the Swift error box of GRB 050223. It is located at z = 0.584 and its luminosity is L ∼ 0.4 L^*. Emission lines in the galaxy spectrum imply an intrinsic {SFR} > 7 M⊙ yr-1, and a large extinction AV > 2 mag within it. We also detect absorption lines, which reveal an underlying stellar population with an age between 40 Myr and 1.5 Gyr.
Conclusions: .The identification of a host galaxy with atypical properties using only the X-ray transient suggests that a bias may be present in the former sample of host galaxies. Dust obscuration together with intrinsic faintness are the most probable causes for the darkness of this burst.

2006 • Astronomy and Astrophysics
XMM-Newton 27
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