TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1578
SUBJECT: GRB 021004: Optical Observations
DATE:    02/10/05 12:08:24 GMT
FROM:    Jules Halpern at Columbia U.  <jules@astro.columbia.edu>

J. P. Halpern, E. K. Armstrong, C. C. Espaillat (Columbia),
J. Kemp (Joint Astronomy Centre and Columbia) report for the
MDM GRB follow-up team:

"We observed the optical afterglow (Fox, GCN #1564) of GRB 021004 with
the MDM 1.3m in BVRI.  On 2002 Oct 5 UT, we measure the following
preliminary magnitudes:

		--------------------
		  UT      R     +/-
		--------------------
		03:02	19.06   0.06
		03:36	19.17   0.05
		04:26	19.24	0.03
		04:51   19.30   0.04
		05:15   19.30   0.03
		05:39   19.25   0.03
		06:10   19.33   0.03
                06:34   19.30   0.04
		06:56   19.32   0.03
                07:19   19.42   0.03
		07:42	19.31	0.03
		08:05   19.31   0.03
		08:28   19.31   0.03
		08:50   19.27   0.03
                09:13   19.29   0.03
		09:41   19.34   0.03
		10:03   19.34   0.03
                10:41   19.41   0.03
		11:04   19.39   0.03
                11:26   19.41   0.04
		11:50   19.39   0.04
		--------------------

We employed the Weidinger et al. (GCN #1573) revised calibration star.
These measurements are consistent with and extend the steepening light
curve that they saw.  The combined NOT and MDM points indicate a decay
slope alpha = 1.16 +/- 0.07, but there are possible fluctuations of the
type referred to by Winn et al. (GCN #1576) in our data that are
contemporaneous with theirs.

An updated decay curve is available at:

http://www.astro.columbia.edu/~jules/021004.ps

An equal number of images in each of B, V, and I were obtained, and will
be analyzed subsequently."