GCN Circular 9462
Subject
GRB 090531B: ROTSE-III Optical Limits
Date
2009-05-31T19:20:55Z (15 years ago)
From
Brad Schaefer at LSU <schaefer@grb.phys.lsu.edu>
B. E. Schaefer (Louisiana State), T. Guver (U Arizona), S. B. Pandey (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 090531B (Swift trigger 353728; J. R. Cummings et al., GCN
9461), producing images beginning 7.3 s after the GCN notice time. An
automated response took the first image at 18:36:22.3 UT, 26.1 s after the
burst, and during the gamma-ray emission, under excellent conditions. We
took 10 5-sec, 10 20-sec and 50 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; however, we are limited as the field is somewhat crowded.
Individual images have limiting magnitudes ranging from 15.3-16.0; we set
the following specific limits.
start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
18:36:22.3 18:36:27.3 5 15.3 26.1 N
18:47:31.3 18:52:11.6 280 16.3 695.1 Y
[GCN OPS NOTE(31may09): Per author's request, the "B" was added
to the burst name.]