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GCN Circular 1587

Subject
GRB 021004: Optical Observations
Date
2002-10-06T07:10:41Z (22 years ago)
From
T.P. Prabhu at Indian Astro. Obs. <tpp@iiap.ernet.in>
D.K. Sahu, B.C. Bhatt, G.C. Anupama, T.P. Prabhu (Indian Institute of
Astrophysics, Bangalore) report on behalf of a larger collaboration:

GRB 021004 was observed with the HFOSC instrument on the 2-m Himalayan
Chandra Telescope on 4 and 5 October 2002. The magnitudes with respect to
the comparison star of Fox (GCN 1564) as calibrated by Henden (GCN 1583)
on October 4 are listed below:

October 4 	   R    error
UT(center)	(300 s)

16:34:36 	17.13	0.01
16:44:03	17.20   0.01
16:52:29	17.24   0.01
17:01:16	17.21   0.01
17:09:26	17.28   0.01
17:18:12	17.39   0.01
18:04:37	17.69   0.01
19:48:36	17.90   0.02
20:33:36	18.06   0.02
22:05:58	18.20   0.03
23:36:22	18.46   0.05

		  B
		(600s)

17:34:18	18.42   0.01
20:01:07	18.90   0.02
22:18:14	19.18   0.03
23:03:11	19.31   0.03

		  V
		(400s)

17:42:32	18.01   0.01
20:14:38	18.50   0.02
22:40:30	18.77   0.03
23:14:33	18.78   0.03

These results supersede the ones reported in GCN 1581. Preliminary
magnitudes for October 5 are

UT	R

17:38	19.38
22:10	19.70

The decay appears to have steepened following the bump noticed by Winn et
al (GCN 1576).

The spectra recorded with the same instrument on October 4 show the
redshift systems with z=1.38 and 1.60 (GCN 1582). The identification of
z=1.72 in GCN 1582 was erroneous and is regretted. On the other hand, we
confirm the presence of unidentified lines reported by Eracleous et al
(GCN 1579).

The message may be cited.
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