[vsnet-grb-info 4750] GRB 070610: OPTIMA-Burst high-time-resolution optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6492
SUBJECT: GRB 070610: OPTIMA-Burst high-time-resolution optical observations
DATE:    07/06/11 00:22:55 GMT
FROM:    Alexander Stefanescu at MPE  <astefan at mpe.mpg.de>

A. Stefanescu (1), A. Slowikowska (2)(3), G. Kanbach (1), S. Duscha (1), 
F. Schrey (1), H. Steinle (1), Z. Ioannou (4) of the OPTIMA-Burst Team 
report the following:
(1)=MPE, Garching, (2)=FORTH, Heraklion (3)=NCAC, Torun (4)=Univ. of Crete

"OPTIMA-Burst at the 1.3m Skinakas Observatory, of the University of
Crete, Greece slewed to the Swift BAT-errorcircle of GRB 070610 (GCN
Circ 6489, C. Pagani et al.) and started observations at 20:53:23UT (57s 
after the burst, 28s after the notice).

We detected a faint transient in the BAT errorcircle. The transient was 
marginally detected as 19+-0.4 mag in our first 10s white-light image, 
and was not detected in subsequent CCD frames. The position of the 
transient is inside the XRT error-circle (GCN 6490, C. Pagani et al.).

At 20:57:19 (293s after the burst) observations with the fibre-fed, 
single-photon-counting high-time-resolution main instrument of 
OPTIMA-Burst started. A quick-look analysis of this data binned to 1s 
resolution indicates that the source is barely detectable (below the 2 
sigma level) until 21:00:22 (476s after the burst). At that time the 
source showed a flaring activity of about 7.5 sigma above the background 
level. The activity lasted about 80s and consisted of three to four 
overlapping spikes and a slow decay.

Further analysis is in progress."

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