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GCN Circular 440

Subject
GRB 991106 Optical Observations
Date
1999-11-08T20:00:09Z (25 years ago)
From
Brian Lindgren Jensen at U.of Copenhagen <brian_j@astro.ku.dk>
B. L. Jensen, H. Pedersen, J. Hjorth, S. Larsen (University of
Copenhagen), and E. Costa (CNR, Rome; on behalf of the BeppoSAX
consortium) report:

Using the ALFOSC instrument at the 2.5-m Nordic Optical Telescope, La
Palma, we have obtained five 2x2 mosaics, covering the error circle
(Piro, GCN #435). All exposures were taken in the R band and lasted 300
s. The first data (three mosaics) were obtained from 6.872 to 6.921 Nov
1999 UT, i.e. starting ~10 hours after the event, and the last (two
mosaics) were obtained from 7.845 to 7.884 Nov 1999 UT. On the first
night the seeing was ~1.4", on the second ~1.4-1.8".

We have compared the exposures both internally and to the DSS-2 (POSS-II
R), finding no variable objects. The limiting magnitude of the first
night's data is approximately R ~ 23.5. The corresponding figure for the
second night is R ~ 22.0 (due to variable cloud cover). Comparison
between the data of the first and second night sets a limit of R ~ 22
(Nov 7.8 1999 UT) on possible optical transients varying by more than
0.5 magnitude (relative to Nov 6.9 Nov 1999 UT).

A .jpg-image of the field can be found at:
http://www.astro.ku.dk/~brian_j/grb/grb991106
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