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GCN Circular 8866

GRB 090201: ROTSE-III Optical Limits
2009-02-01T19:01:36Z (15 years ago)
Brad Schaefer at LSU <>
B. E. Schaefer (Louisiana State) reports on behalf of the ROTSE 

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 090201 (Swift trigger 341749; S. R. Oates et al., GCN
8865), producing images beginning 41 minutes after the burst trigger.  
Weather constraints in Namibia were the cause of the delay, as we had to
await the clearing of the skies.  Our first image was at 18:28:03.6 UT,
2460.9 s after the burst, under fair conditions. We took 10 5-sec, 10
20-sec and -8 60-sec exposures. These unfiltered images are calibrated
relative to USNO A2.0 (R). Imaging is on going.

Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma Swift/BAT error circle, for both single images and coadding into
sets of 10; the field is not crowded.  Swift has not slewed to this burst
yet, so there is no XRT position to examine in detail.  Individual images
have limiting magnitudes ranging from 16.6-17.4; we set the following
specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
18:28:03.6   18:29:03.6        60     16.6         2460.9       N
18:28:03.6   18:30:15.5       131     16.9         2460.9       Y
18:42:25.4   18:54:11.1       705     18.2         3322.7       Y
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