[vsnet-grb-info 6928] GRB 081109: TAROT La Silla observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8517
SUBJECT: GRB 081109: TAROT La Silla observatory optical observations
DATE:    08/11/12 09:21:09 GMT
FROM:    Alain Klotz at CESR-CNRS  <Alain.Klotz at free.fr>

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

We imaged the field of GRB 081109 detected by SWIFT
(trigger 334112) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 29.4s after the GRB trigger.
The elevation of the field decreased from
11 degrees above horizon and weather conditions
were excellents.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect the afterglow mentioned by D'Avanzo et
al. (GCNC 8501) with a limiting magnitude of:

t0+29.4s to t0+89.4s : R > 16.9

This image was taken during the gamma emission.
This means that there was no bright optical flash
associated to this burst.

The second image is 30.0s exposure in tracking mode.
We detect the afterglow:

t0+95.1s to t0+125.1s : R ~ 17.8 +/- 0.2

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

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