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GCN Circular 5747

GRB 061021 - VLT spectrum without lines
2006-10-22T17:57:23Z (18 years ago)
Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr <>
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

An image of the 2D spectrum can be found at

We thank the staff at VLT for performing the observations, especially G.
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