[vsnet-grb-info 2457] GRB 051021 Optical Observations

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4294
SUBJECT: GRB 051021 Optical Observations
DATE:    05/11/20 05:37:23 GMT
FROM:    T.P. Prabhu at Indian Astro. Obs.  <tpp at crest.ernet.in>

D.K. Sahu, G. Pandey, P. Bama and N.K. Chakradhari (Indian Institute of
Astrophysics, Bangalore,India) communicate on behalf of a larger Indian
collaboration:

We observed the error box of the HETE trigger 3947 in Bessell R and I
filters with the 2-m Himalayan Chandra Telescope, Hanle, India, between
20:25 UT and 21:00 UT, 2005 October 21 (about 7 hours after the burst).
We could clearly detect the OT of GRB 051021 reported by Fox et al. (GCN
4120) with effective exposures of 600s (2x300s) in R and 900s (3x300s) in
I band.  The preliminary magnitudes for the OT, estimated using the
calibration provided by Henden (GCN 4184) are as follows:

Filter    Mean Mid-UT     Magnitude
  R          20:43      21.51+/-0.15
  I          20.43      20.93+/-0.10

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