GCN Circular 5747
Subject
GRB 061021 - VLT spectrum without lines
Event
Date
2006-10-22T17:57:23Z (20 years ago)
From
Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr <cthoene@astro.ku.dk>
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.