[vsnet-grb-info 4088] GRB 061202: TORTOREM optical upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5897
SUBJECT: GRB 061202: TORTOREM optical upper limits
DATE:    06/12/05 10:46:45 GMT
FROM:    Giuseppe Greco at U Bologna  <giuseppe.greco2 at studio.unibo.it>

S. Karpov, G. Beskin, S. Bondar, C. Bartolini, G. Greco, A. Guarnieri,
D. Nanni, A. Piccioni, F. Terra, E. Molinari, G. Chincarini, F.M. Zerbi,
S. Covino, V. Testa, G. Tosti, F. Vitali, L.A. Antonelli, P. Conconi,
G. Cutispoto, G. Malaspina, L. Nicastro, E. Palazzi, E. Meurs, P. Goldoni
report on behalf of the TORTOREM team:

The field of GRB 061202 (Sakamoto et al. GCN 5886) has been observed
by the TORTORA (Telescopio Ottimizzato per la Ricerca di Transienti
Ottici RApidi) wide-field fast camera (12 cm diameter, 20x25 deg FOV)
mounted on REM robotic 60-cm telescope located at La Silla (Chile). 
The burst was outside the camera field of view. The system was repointed
and the TORTORA began to acquire frames at 08:13:16 UT 
(92 sec after trigger) with 7.5 Hz frame frequency (0.128 s exposure).

The summation of 100 frames with 12.8 s. effective exposure 
did not reveal any source down to the B = 11.3 mag (3-sigma)
on bright sky background.

We performed the Fourier analysis of 10 min data set to search for the
periodic signal at the GRB position. The upper limit for the amplitude
of sinusoidal variability is B=14.0 (1-sigma) over the 0.1 - 3.5 Hz
range.

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