[vsnet-grb-info 3971] GRB 061027: TAROT La Silla observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5788
SUBJECT: GRB 061027: TAROT La Silla observatory optical observations
DATE:    06/11/08 08:24:06 GMT
FROM:    Alain Klotz at CESR-CNRS  <Alain.Klotz at free.fr>

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 061027 detected by SWIFT
(trigger 235645) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

This trigger was long, had no high-energy emission,
it was detected by "image trigger" (Stamatikos et al. GCNC 5760)
and UVOT limiting mag. is V=20.4 until two hours
after the burst. This is a good high-redshift candidate, so
we shot a series of filtered R and I exposures centered
on the BAT refined position (Parsons et al. GCNC 5761).

The observations started 14.0h after the GRB trigger.
The elevation of the field decreased from from 33 degrees
above horizon and weather conditions were excellent.
We obtained a second set of exposures on 2006 nov. 7 for
comparison and to extract fading sources.

The date of trigger : t0 = 2006-10-27T10:15:02.304

We co-added series of filtered exposures, and we do
not detect any OT:

t0+14.0h to t0+18.6h : R > 20.0 and I > 18.9

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon=311.3409 lat=-25.2566
and the galactic extinction in R band is 0.1 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

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