The host galaxy and optical light curve of the gamma-ray burst GRB 980703 *,**,***
Institute of Physics and Astronomy, University of Aarhus, 8000 Århus C., Denmark e-mail: firstname.lastname@example.org
2 Department of Physics, University of Notre Dame, Notre Dame, IN 46556-5670, USA e-mail: email@example.com
3 European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany e-mail: firstname.lastname@example.org; email@example.com
4 Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark e-mail: firstname.lastname@example.org; email@example.com
5 Danish Space Research Institute, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark e-mail: firstname.lastname@example.org
6 Division of Astronomy, University of Oulu, PO Box 3000, 90014 Oulu, Finland e-mail: email@example.com
7 Department of Physics, Technion, Haifa 32000, Israel e-mail: firstname.lastname@example.org
8 Science Institute, Dunhagi 3, University of Iceland, 107 Reykjavik, Iceland e-mail: email@example.com
9 European Southern Observatory, Casilla 19001, Santiago 19, Chile e-mail: firstname.lastname@example.org
10 Department of Astronomy, Yale University, New Haven, CT 06520-8181, USA e-mail: email@example.com
11 Department of Physical Sciences, University of Hertfordshire, College Lane, Hatfield, Hertfordshire, AL10 9AB, UK e-mail: firstname.lastname@example.org
Corresponding author: S. Holland, email@example.com
Accepted: 27 February 2001
We present deep HST/STIS and ground-based photometry of the host galaxy of the gamma-ray burst GRB 980703 taken 17, 551, 710, and 716 days after the burst. We find that the host is a blue, slightly over-luminous galaxy with , , and a centre that is ≈ 0.2 mag bluer than the outer regions of the galaxy. The galaxy has a star-formation rate of 8-13 , assuming no extinction in the host. We find that the galaxy is best fit by a Sersic profile with and a half-light radius of ( proper kpc). This corresponds to an exponential disk with a scale radius of ( proper kpc). Subtracting a fit with elliptical isophotes leaves large residuals, which suggests that the host galaxy has a somewhat irregular morphology, but we are unable to connect the location of GRB 980703 with any special features in the host. The host galaxy appears to be a typical example of a compact star forming galaxy similar to those found in the Hubble Deep Field North. The R-band light curve of the optical afterglow associated with this gamma-ray burst is consistent with a single power-law decay having a slope of . Due to the bright underlying host galaxy the late time properties of the light-curve are very poorly constrained. The decay of the optical light curve is consistent with a contribution from an underlying type Ic supernova like SN1998bw, or a dust echo, but such contributions cannot be securely established.
Key words: supernovae: individual / galaxies: individual / galaxies: photometry / galaxies: structure / gamma rays: bursts
Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
Based on observations made with the Nordic Optical Telescope (NOT), operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden.
© ESO, 2001