Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 611

GRB000301C - B and R photometry
2000-03-14T23:57:10Z (24 years ago)
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 OSIS 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 

R = 23.82 +/- 0.10   2000 March 14.60 (UTC) 
(two 30mn exposures) 

B = 24.83 +/- 0.12   2000 March 14.60 (UTC) 
(one 55mn exposure) 

The power-law decay described with alpha = -2.1 +/- 0.1 (GCN610) is not
sufficient to account properly for the last four measurements (GCN598, 
604, 610 and this GCN), which are better fit with alpha = -2.7 +/- 0.1 . 
The first phase of the decay would cover the first four days after the 
burst, with alpha = -0.91 +/- 0.08. A graph with these two consecutive 
power laws, as well at the new images, are at 

As for the apparent B-R, the error bars are large enough to make it close 
to the value determined using MOS on March 3.5 (0.86 +/- 0.06) or the one 
published by Halpern (0.77 +/- 0.06 in GCN585 a week ago). 

As the GRB is still steadily decaying, it's unlikely to have the underlying
galaxy contributing significantly to the measured flux. This galaxy should 
probably be fainter than R = 24.5, confirming the comment by Fruchter et al. 
(GCN602) from HST imaging data (R >~ 24). 

A 20 micron camera will be installed on the telescope today for 10 nights. 
No new data on this GRB will be acquired during this period. 

Aloha from Hawaii! 

I. Gable is acknowledged for his help in this observation. 

This message may be cited. 
Dr. Christian Veillet,       CFHT Senior Resident Astronomer
Phone: (808) 885-3161
Looking for U.S. government information and services? Visit