GCN Circular 6561
Subject
GRB 070621: ROTSE-III Prompt Optical Limits
Date
2007-06-21T23:46:58Z (17 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
E.S. Rykoff (U Mich), W. Rujopakarn (Steward), B. E. Schaefer (Louisiana
State), H. Swan (U Mich), J. Aretakis (U Mich), R. Quimby (U Texas),
report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 070621 (Swift trigger 282808, Sbarufatti, et al., GCN
6560), producing images beginning 6.1 s after the GCN notice time. An
automated response took the first image at 23:18:03.1 UT, 23.3 s after
the burst, and during gamma-ray emission. We took 10 5-sec, 10 20-sec
and 10 60-sec exposures. These unfiltered images are calibrated relative
to USNO A2.0 (R). Imaging is ongoing.
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma Swift/BAT error circle or the XRT error circle, for both single
images and coadding into sets of 10. Individual images have limiting
magnitudes ranging from 16.4-17.8; we set the following specific limits.
start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
23:18:03.1 23:18:08.1 5 16.6 23.3 N
23:18:03.1 23:19:20.7 77 17.5 23.3 Y
23:19:28.5 23:24:16.3 287 18.5 108.7 Y
23:24:25.7 23:35:51.6 685 18.8 405.9 Y