[vsnet-grb-info 442] GRB 021004: Optical Photometry at 1.5 Days

[GCN Circulars <gcncirc@lheawww.gsfc.nasa.gov>]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1585
SUBJECT: GRB 021004: Optical Photometry at 1.5 Days
DATE:    02/10/06 02:29:36 GMT
FROM:    Stephen Holland at U. of Notre Dame  <sholland@nd.edu>

GRB 021004: Optical Photometry at 1.5 Days

S. Holland (Notre Dame), J. P. U. Fynbo, M. Weidinger (Aarhus)
M. P. Egholm (NOT), and A. Levan (Leicester)
on behalf of a larger collaboration report:

     We have obtained deep R-band images of the field containing
GRB 021004 using the 2.56-meter Nordic Optical Telescope on La Palma
on Oct. 6.0 UT.  The optical afterglow of GRB 011211 is visible in our
images.  Using the comparison star from Fox et al. (2002, GCN 1564)
and the calibration of Henden (2002, GNC 1583) we find the following
preliminary magnitudes:

          Date       UT     t(days)   Rc   Err
          -------------------------------------
          Oct. 5  20:24:58   1.346   19.54 0.04
          Oct. 5  20:36:28   1.354   19.53 0.04
          Oct. 5  22:22:31   1.428   19.62 0.05
          Oct. 6  00:10:41   1.503   19.66 0.04

     These magnitudes imply that the optical afterglow faded at a rate
of alpha = -1.08 during the four hours that these observations were
taken.  Combining these magnitudes with those of Weidinger et al.
(2002, GCN 1573) suggests that the optical afterglow has decayed with
a constant slope of alpha = -1.01 between 0.09 and 1.50 days after the
burst.  A plot of our preliminary Rc-band light curve is available at
<http://www.nd.edu/~sholland/grb/grb021004/lightcurve1.eps>.

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