GCN Circular 5747
Christina C. Thoene, Johan P.U. Fynbo (DARK) and Pall Jakobsson (Univ. of Hertfordshire) report on behalf of a larger collaboration: We obtained a single 1800s spectrum of the OT of GRB 061021 (GCN 5743) on October 22, 08:07UT, 16.5h after the burst, using FORS1/VLT and grism 300V. At the time of the observation, the OT had a magnitude of about R=20.5, based on photometric zeropoints from the ESO webpages. The spectrum displayed a smooth continuum with no emission or absorption lines, although the S/N of the source was resonably high. From the lack of the Ly-alpha forest, a firm upper limit of z<2.0 can be placed on the redshift of the GRB. This is consistent with the UVOT observations (GCN 5745). An image of the 2D spectrum can be found at www.astro.ku.dk/~cthoene/GRBs/ We thank the staff at VLT for performing the observations, especially G. James.