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arXiv · astro-ph/0609444

GRB 050223: A dark GRB in a dusty starburst galaxy

L. J. Pellizza·P. -A. Duc·E. Le Floc'h·I. F. Mirabel·L. A. Antonelli·S. Campana·G. Chincarini·A. Cimatti·S. Covino·M. Della Valle·F. Fiore·D. Fugazza·P. Giommi·P. Goldoni·G. L. Israel·E. Molinari·A. Moretti·L. Piro·P. Saracco·L. Stella·G. Tagliaferri·M. Vietri
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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 Msun/yr, and a large extinction A_V > 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.

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L. J. Pellizza, P. -A. Duc, E. Le Floc'h, I. F. Mirabel, L. A. Antonelli, S. Campana, G. Chincarini, A. Cimatti, S. Covino, M. Della Valle, F. Fiore, D. Fugazza, P. Giommi, P. Goldoni, G. L. Israel, E. Molinari, A. Moretti, L. Piro, P. Saracco, L. Stella, G. Tagliaferri, M. Vietri. 2006-09-15. GRB 050223: A dark GRB in a dusty starburst galaxy. https://doi.org/10.1051/0004-6361%3A20066015

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