EDP Sciences
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Volume 413, Number 1, January I 2004
Page(s) 121 - 130
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20031517

A&A 413, 121-130 (2004)
DOI: 10.1051/0004-6361:20031517

The host galaxy of GRB 990712

L. Christensen1, J. Hjorth2, J. Gorosabel3, 4, 5, P. Vreeswijk6, 7, A. Fruchter8, K. Sahu8 and L. Petro8

1  Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
2  Niels Bohr Institute, Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
3  Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada, Spain
4  Laboratorio de Astrofísica Espacial y Física Fundamental (LAEFF-INTA), PO Box 50727, 28080 Madrid, Spain
5  Danish Space Research Institute, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
6  European Southern Observatory, Casilla 19, Santiago, Chile
7  Astronomical Institute "Anton Pannekoek", University of Amsterdam & Center for High Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
8  Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

(Received 23 December 2002 / Accepted 20 September 2003 )

We present a comprehensive study of the z=0.43 host galaxy of GRB 990712 , involving ground-based photometry, spectroscopy, and HST imaging. The broad-band $U\!BV\!RI\!J\!H\!K$s photometry is used to determine the global spectral energy distribution (SED) of the host galaxy. Comparison with that of known galaxy types shows that the host is similar to a moderately reddened starburst galaxy with a young stellar population. The estimated internal extinction in the host is $A_V=0.15\pm 0.1$ and the star-formation rate (SFR) from the UV continuum is 1.3  $\pm$ 0.3  M $_{\normalsize\odot}$ $\>\rm yr^{-1}$ (not corrected for the effects of extinction). Other galaxy template spectra than starbursts failed to reproduce the observed SED. We also present VLT spectra leading to the detection of H $\alpha$ from the GRB host galaxy. A SFR of 2.8  $\pm$ 0.7  M $_{\normalsize\odot}$ $\>\rm yr^{-1}$ is inferred from the H $\alpha$ line flux, and the presence of a young stellar population is supported by a large equivalent width. Images from HST/STIS show that the host has two separate knots, which could be two distinct star-forming regions.

Key words: gamma rays: bursts -- galaxies: hosts -- galaxies: star formation

Offprint request: L. Christensen, lchristensen@aip.de

SIMBAD Objects

© ESO 2004