GCN Circular 3867
Subject
GRB 050824: ROTSE-III Optical Limits
Date
2005-08-25T01:58:31Z (19 years ago)
From
Brad Schaefer at LSU <schaefer@grb.phys.lsu.edu>
B. E. Schaefer (Louisiana State), Fang Yuan (U Mich), and K. Alatalo
(Berkeley) report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 050824 (Swift trigger 151905), producing images beginning
7.1 s after the GCN notice time. An automated response took the first
image at 23:22:02.1 UT, 585.8 s after the burst, under good conditions
although with the gibbous Moon only 25 degrees away. We took 10 5-sec, 10
20-sec and 130 60-sec eposures. These unfiltered images are calibrated
relative to USNO A2.0 (R).
ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe,
Turkey, also responded, producing images beginning 5.8 s after the GCN
notice time. An automated response took the first image at 23:22:00.8 UT,
584.5 s after the burst, under good conditions (but again, with the
gibbous Moon nearby). We took 10 5-sec, 10 20-sec and 80 60-sec eposures.
These unfiltered images are also calibrated relative to USNO A2.0 (R).
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma error circle, for both single images and coadding into sets of 10.
Individual images have limiting magnitudes ranging from 15.4-17.0; we set
the following specific limits.
ROTSE start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------------
III-c 23:22:02.1 23:23:27.1 85 17.3 585.8 Y
III-c 23:23:27.7 23:28:21.7 294 18.2 671.4 Y
III-d 23:22:00.8 23:24:20.8 140 17.4 584.5 Y
III-d 23:24:21.5 23:29:20.5 299 17.9 725.2 Y
In particular, we do not see the new source described by Gorosabel et al.
(GCN 3865), with this source being near or below our detection threshold.