[vsnet-grb-info 3929] GRB 061025: ROTSE-III Optical Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5752
SUBJECT: GRB 061025: ROTSE-III Optical Limits 
DATE:    06/10/25 19:55:31 GMT
FROM:    Eli Rykoff at U of Michigan/ROTSE  <erykoff at umich.edu>

E.S. Rykoff (U Mich), B. E. Schaefer (Louisiana State), R. Quimby (U 
Texas), H. Swan (U Mich), S.A. Yost (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 061025 (Integral trigger 3525, Mereghetti, et al, GCN 
5751), producing images beginning 4.6 s after the GCN notice time. An 
automated response took the first image at 18:36:46.6 UT, 44.7 s after 
the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 
31 60-sec eposures. These unfiltered images are calibrated relative to 
USNO A2.0 (R).

Comparison to the DSS (second epoch) reveals no new sources within the 
90% INTEGRAL error circle, for both single images and coadding into sets 
of 10; however, we are limited as the field is somewhat crowded.  We 
note that the bright elliptical galaxy NGC 6851 is in the error box. 
Individual images have limiting magnitudes ranging from 13.3-16.9; we 
set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
18:36:46.6   18:36:51.6         5     15.2           44.7       N
18:36:46.6   18:39:01.9       135     16.9           44.7       Y
18:39:11.4   18:43:57.0       285     17.5          189.5       Y