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GCN Circular 5213

GRB 060604A: ROTSE-III Optical Limits
2006-06-04T19:06:43Z (18 years ago)
Brad Schaefer at LSU <>
B. E. Schaefer (Louisiana State) reports on behalf of the ROTSE 

ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded to 
GRB 060604A (Swift trigger 213486), producing images beginning 5.0 s after 
the GCN notice time. An automated response took the first image at 
18:19:59.1 UT, 59.0 s after the burst, under excellent conditions. We took 
10 5-sec, 10 20-sec and 20 60-sec eposures, with more ongoing. These 
unfiltered images are calibrated relative to USNO A2.0 (R).

Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma error circle, for both single images and coadding into sets of 10;  
the field is not crowded.  The XRT position and the UVOT position (M. J.  
Page et al. 2006, GCN 5212) has two faint stars nearby which might mask
the fast fading optical transient.  Individual images have limiting
magnitudes ranging from 15.2-16.9; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
18:19:59.1   18:20:19.1        20     15.8           59.0       N
18:29:37.6   18:41:55.8       738     17.9          637.5       Y
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