TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3433
SUBJECT: GRB 050520: VLT/ULTRACAM observations
DATE:    05/05/20 03:43:33 GMT
FROM:    Paul Vreeswijk at ESO  <pvreeswi@eso.org>

P. Vreeswijk (ESO), T. Marsh (U. Warwick), S. Littlefair, V. Dhillon
(U. Sheffield), K. O'Brien (ESO) report on behalf of a larger collaboration:

We observed the central 2.3'x2.3' of the field of GRB 050520 (INTEGRAL
trigger 2505) with the high-time resolution imaging instrument ULTRACAM,
currently attached to the visitor focus of VLT/Melipal. The ULTRACAM
pointing covers about 70% of the INTEGRAL error circle (see Gotz et al.,
GCN 3430). The observations started at 00:18:21 UT (12.5 minutes after the
trigger), and were performed in u', g' and r' simultaneously. The field
was exposed for about 15 minutes, with a sampling time of one second,
which is basically the same as the exposure time due to the negligible
read-out time. Comparison of the individual exposures with the DSS-II
reveals no obvious new source. Moreover, we looked for variability by
combining all exposures (~1000) into 10 sets of 100 individual exposures
each, and subtracting these off one other. Again, no obvious counterpart
is detected.

For more information on ULTRACAM, see:

    http://www.shef.ac.uk/physics/people/vdhillon/ultracam/