[vsnet-grb-info 13938] GRB 130925A: TAROT La Silla observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15252
SUBJECT: GRB 130925A: TAROT La Silla observatory optical observations
DATE:    13/09/25 13:27:30 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz at free.fr>

Klotz A. (IRAP-CNRS-OMP), Gendre B. (IRAP-CNRS-OMP),
Boer M., Siellez K., Dereli H., Bardho O. (UNS-CNRS-OCA),
Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 130925A detected by SWIFT
(trigger 571830) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 88.1s after the GRB trigger
(13.0s after the notice). The elevation of the field increased from
50 degrees above horizon and weather conditions
were good.

We do not detect the afterglow discovered by Sudilovsky
et al. (GCNC 15247, GCNC 15250) and confirmed by Vreeswijk
et al. (GCNC 15249). However, the observations of TAROT
give upper optical limits of the early afterglow.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39):
t0+88.1s to t0+148.1s : Rlim = 17.5

We co-added a series of exposures with diurnal drift:
t0+477s to t0+1081s : Rlim = 19.2

Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.