1 Introduction

Gamma-ray bursts (GRBs) are flashes of cosmic high energy ($\sim$1  ${\rm keV} - 10$ GeV) photons (Fishman & Meegan 1995). For many years since their discovery in 1967 they remained without any satisfactory explanation, but with the advent of the Italian-Dutch X-ray satellite BeppoSAX, it became possible to conduct deep counterpart searches only a few hours after a burst was detected. This led to the first detection of X-ray and optical afterglow for GRB 970228 (Costa et al. 1997; van Paradijs et al. 1997) and the determination of the cosmological distance scale for the bursts on the basis of the first spectroscopic measurements taken for GRB 970508, implying z $\geq$ 0.835 (Metzger et al. 1997).

Subsequent observations in 1997-2000 have shown that about a third of the well localized GRBs can be associated with optical emission that gradually fades away over weeks to months. Now it is widely accepted that long duration GRBs originate at cosmological distances with energy releases of 10⁵¹-10⁵³ ergs. The observed afterglow satisfies the predictions of the "standard'' relativistic fireball model, and the central engines that power these extraordinary events are thought to be the collapse of massive stars (see Piran 1999; van Paradijs et al. 2000 for a review).

The detection of GRB host galaxies is essential in order to understand the nature of hosts (morphology, star forming rates) and to determine the energetics of the bursts (redshifts) and offsets with respect to the galaxy centres. About 25 host galaxies have been detected so far, with redshifts z in the range 0.43-4.50 and star-forming rates in the range 0.5-60 $M_{\odot}$year^-1. See Klose (2000), Castro-Tirado (2001) and references therein.

Here we report the detection of the optical afterglow from GRB 991208 as well as its host galaxy. This GRB was detected at 04:36 universal time (UT) on 8 Dec. 1999, with the Ulysses GRB detector, the Russian GRB Experiment (KONUS) on the Wind spacecraft and the Near Earth Asteroid Rendezvous (NEAR) detectors (Hurley et al. 2000) as an extremely intense, 60 s long GRB with a fluence >25 keV of 10^-4 ergcm^-2 and considerable flux above 100 keV. Radio observations taken on 1999 December 10.92 UT with the Very Large Array (VLA) at 4.86 GHz and 8.46 GHz indicated the presence of a compact source which became a strong candidate for the radio afterglow from GRB 991208 (Frail et al. 1999).