GCN Circular 2817

J. Wren, W.T. Vestrand, P. Wozniak, R. White, report on behalf of the 
RAPTOR team.

Stereoscopic observations collected by the RAPTOR wide-field sky monitoring 
systems allow us to place optical limits on a prompt optical flash from GRB 
041016 (HETE trigger 3578).  The earliest images were 10 second exposures 
obtained starting at 04:40:13.3 UT (35 seconds after the GRB trigger) with 
a limiting magnitude of R ~ 13.1 mag.  When compared to our later follow-up 
images and sky patrol images taken earlier in the evening, no new or 
variable objects were detected (other than known 
asteroids).  Straightforward extrapolation of the light curve for prompt 
optical emission measured from GRB 021211, an event with approximately half 
the 25-300 keV fluence of GRB 041016, predicts an optical flux that exceeds 
these early flux limits.