TITLE:   GCN CIRCULAR
NUMBER:  6816
SUBJECT: GRB 070920B: TAROT La Silla observatory optical observations
DATE:    07/09/22 06:09:32 GMT
FROM:    Alain Klotz at CESR-CNRS  <Alain.Klotz@free.fr>

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

We imaged the field of GRB 070920B detected by SWIFT
(trigger 291728) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 2.7h after the GRB trigger
(beginning of the night). The elevation of the field increased from
from 27 degrees above horizon and weather conditions
were good but the moon (phase=0.58) was only at 68 degrees
of the field, limiting the detectivity.

We co-added a series of 8 x 180s unfiltered exposures.
We do not detect any OT in the refined position
provided by Barthelmy et al. (GCNC 6811) nor the source
reported by de Ugarte Postigo et al. (GCNC 6809):

t0+2.7h to t0+3.6h : R > 18.2

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction
(which is very low along the line of sight).

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