[AAVSO-HEN] GRB 070611: ROTSE-III Optical Limits

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  6495
SUBJECT: GRB 070611: ROTSE-III Optical Limits
DATE:    07/06/11 02:31:23 GMT
FROM:    Brad Schaefer at LSU  <schaefer at grb.phys.lsu.edu>

Bradley E. Schaefer (Louisiana State), S.A. Yost (U Mich), E.S. Rykoff (U 
Mich), and F. Yuan (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 070611 (Swift trigger 282003; M. C. Stroh et al. 2007,
GCN 6494), producing images beginning 7.6 s after the GCN notice time. An
automated response took the first image at 01:57:58.6 UT, 44.7 s after the
burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 20
60-sec exposures, with further exposures now ongoing. These unfiltered
images are calibrated relative to USNO A2.0 (R).

Comparison to the DSS (second epoch) reveals no new sources within the 
3-sigma Swift/BAT error circle; the field is not crowded. Individual 
images have limiting magnitudes ranging from 15.7-17.2; we set the 
following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
01:57:58.6   01:58:03.6         5     15.8           44.7       N
01:57:58.6   01:59:16.6        78     17.0           44.7       Y
02:04:20.5   02:15:45.2       684     18.3          426.6       Y