TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1614 SUBJECT: GRB 021004: Optical observations, AUDE network DATE: 02/10/10 07:16:20 GMT FROM: Michel Boer at CESR-CNRS A. Klotz and M. Boer, CESR/CNRS (Centre d'Etude Spatiale des Rayonnements, Toulouse, France) report measurements obtained by members of the AUDE network (Association des Utilisateurs de Detecteurs Electroniques). As images were not filtered, the authors computed the magnitudes in reference to the R band system which is expected to be the most reliable for unfiltered CCD images. Magnitudes of GRB 021004 : 2002 oct. 5, 01h04 UT : R=18.8 by R. Poncy (1) 2002 oct. 5, 22h30 UT : R=19.70 +/- 0.1 (referenced to USNO) by P. Martinez & P.M. Berger (2) (1) Diam. 254 mm Integ. 30 x 60 sec. Location : Le Cres, France (IAU station 177) (2) Diam. 820 mm Integ. 23 x 60 sec. Location : ADAGIO observatory, Belesta, France (IAU station A05) Note also a detection of the optical counterpart at 2002 oct. 5, 21h30 UT, by A. Klotz using a telescope of only 200 mm diameter. Low signal to noise did not allow to measure the magnitude, but the limiting magnitude of the image is about 20.5 (addition of 60 frames of 60 sec). This demonstrates that small telescopes can detect the afterglow of a GRB even 1.4 days after the GRB event. Images are available at the following URL: http://www.cesr.fr/~klotz/grb021004/aude.html These data are coherent with already reported magnitude in other circulars, and fill some gaps in the light curve.