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GCN Circular 3107

GRB 050306: ROTSE-III early limits
2005-03-16T23:13:55Z (19 years ago)
Robert Quimby at U of Texas/ROTSE <>
R. M. Quimby, E. S. Rykoff, B. E. Schaefer, D. A. Smith and S. A. Yost
report on behalf of the ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded automatically to Swift GRB 050306 (Markwardt et al., GCN
3071) with the first 5-second exposure beginning Mar 6, 03:34:16.7 UT,
64.8 seconds after the burst. Comparison to the DSS (second epoch)
reveals no new sources, but we are limited by crowding in this low
galactic latitude field.

Using software provided by the Supernova Cosmology Project, we have
subtracted ROTSE-IIIc data obtained on Mar. 8 from our first Mar 6
image. No sources are detected on the subtracted frame within the
Swift XRT error circle (Perri et al., GCN 3075). In particular, we set
a 3-sigma upper limit on the magnitude of 15.8 (unfiltered, relative
to USNO A2.0) at the location of the TNG source (D'Avanzo et al., GCN

An extrapolation of a simple power-law with an index of 1.28 from the
TNG detection back to the epoch of our first image would predict a ~12
mag source. However, our non-detection is consistent with other
optical light curves that are underluminous at early times such as
GRBs 030418 and 030723 (Rykoff et al., 2004 ApJ 601,1013)
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