TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5298 SUBJECT: GRB 060707: OA fading and redshift DATE: 06/07/09 19:05:24 GMT FROM: Pall Jakobsson at U Hertfordshire Pall Jakobsson, Nial Tanvir (Univ. of Hertfordshire), Brian L. Jensen, Johan P. U. Fynbo (DARK, NBI), Antonio de Ugarte Postigo, Javier Gorosabel (IAA-CSIC Granada), Sylvio Klose (TLS Tautenburg) and Paul Vreeswijk (ESO) report on behalf of a larger collaboration: Using FORS1 on the Very Large Telescope, we have obtained 3*30 min spectra (300V) of the GRB 060707 field (Moretti et al., GCN 5285). The acquisition image shows that the proposed optical afterglow (de Ugarte Postigo et al., GCN 5290) has faded by approximately two magnitudes. Using photometric zeropoints from the ESO webpages we estimate the afterglow magnitude to be R ~ 22.4 on July 9.329 (1.432 days post-burst). The combined spectrum displays a strong absorption feature around 5386 AA, with the flux dropping substantially blueward of this feature. Associating it with Ly-alpha gives a redshift of z = 3.43 for the burst. At this redshift we find several other absorption features, including Ly-beta, Si II, Si IV, C IV, Al II and O III].