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GCN Circular 6495

GRB 070611: ROTSE-III Optical Limits
2007-06-11T02:31:23Z (17 years ago)
Brad Schaefer at LSU <>
Bradley E. Schaefer (Louisiana State), S.A. Yost (U Mich), E.S. Rykoff (U 
Mich), and F. Yuan (U Mich) report on behalf of the ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 070611 (Swift trigger 282003; M. C. Stroh et al. 2007,
GCN 6494), producing images beginning 7.6 s after the GCN notice time. An
automated response took the first image at 01:57:58.6 UT, 44.7 s after the
burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 20
60-sec exposures, with further exposures now 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 Swift/BAT error circle; the field is not crowded. Individual 
images have limiting magnitudes ranging from 15.7-17.2; we set the 
following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
01:57:58.6   01:58:03.6         5     15.8           44.7       N
01:57:58.6   01:59:16.6        78     17.0           44.7       Y
02:04:20.5   02:15:45.2       684     18.3          426.6       Y
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