1 Introduction

There are two, possibly fundamentally different, classes of gamma-ray bursts (GRBs) - short and long duration bursts (being shorter and longer than $\sim$1 s respectively). So far every GRB with an identified optical afterglow (OA) belongs to the class of long duration bursts, with the possible exception of GRB 000301C (Jensen et al. 2001). There are two general types of models for producing GRBs, the first involves the merging of binary compact stars (Paczynski 1986), the second is related to the death of very massive stars (Woosley 1993; MacFadyen & Woosley 1999; Vietri & Stella 1998). The observations of SN bumps, Fe K-line and OA localizations close to star-forming regions favour the latter type of models for long bursts. Due to the relatively short lifetime of such massive stars, one expects them to be located in or very close to star-forming regions where they are born. Thanks to the extensive observational efforts in pursuing GRB events at various wavelengths there are now several examples where such positional correlations between the GRB OA and star forming regions in the host are seen, for instance Fynbo et al. (2000) (GRB 980425), Holland & Hjorth (1999) (GRB 990123), Hjorth et al. (2002) (GRB 980613), Fynbo et al. (2002) (GRB 000926), Bloom et al. (2001), Chary et al. (2002) and Frail et al. (2002) (GRB 010222). There are, however, a few cases in which the GRB does not seem to originate from intense star-forming regions (SFRs), e.g. GRB 990705 (Andersen et al. 2002).

In this paper we present localisations and host candidates of three OAs using ground-based data and Hubble Space Telescope (HST) STIS imaging data from the Cycle 9 program GO-8640 "A Public Survey of the Host Galaxies of Gamma-Ray Bursts'' (Holland et al. 2000) (data and further information available at http://www.ifa.au.dk/~hst/grb_hosts/index.html). These results supersede any preliminary results reported by us in GCN Circulars. In Sect. 2 we describe the image processing applied to the data, in Sect. 3 the astrometry resulting in the OA STIS-image localisations is described. In Sects. 4-6 we identify the hosts, present photometry and discuss the host environment. Finally, in Sect. 7 we discuss the implications of our localisations and host identifications. Specifically, we re-compute using our host identifications, the probability computed in Bloom et al. (2002) that none of the host identifications in that sample are random galaxies. Finally, we summarize our own results.