TITLE: GCN GRB OBSERVATION REPORT NUMBER: 598 SUBJECT: GRB000301c - R photometry and nearby faint source confirmation DATE: 00/03/07 22:57:59 GMT FROM: Christian Veillet at CFHT The candidate for the optical transient (OT) associated with the gamma ray burst GRB000301c has been observed in imaging mode with MOS on the 3.6-m CFH Telescope in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT). The OT has the following magnitude, using star A (GCN573) photometry (GCN583): R = 21.70 +/- 0.07 2000 March 7.65 (UTC) This value does not fit very well with the the R magnitudes published in the previous GCN, in particular by Mohan(595), if we assume a power law common to all observations. In fact, the best fit of the data published so far is obtained with a linear magnitude decay of 0.32 +/- 0.02 mg/day... The acceleration in the decay in K (GCN596) seems also to be seen in R. More data, as well as a careful reanalysis of the existing images, are clearly needed! The faint source found on March 5 (GCN592), recognized in GCN594 as identical to the one detected in IR at NASA IRTF, is definitely there also on the March 7 image. A composite of the two images is available at http://www.cfht.hawaii.edu/~veillet/grb.html . Its R magnitude is measured as 24.3 +/- 0.3 , to be refined with further analysis. S. Lilly is acknowledged for his help in this observation. This message may be cited. -- ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************