[vsnet-grb-info 12423] GRB 120923A: TAROT La Silla observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13798
SUBJECT: GRB 120923A: TAROT La Silla observatory optical observations
DATE:    12/09/23 06:00:56 GMT
FROM:    Alain Klotz at CESR-CNRS  <Alain.Klotz at free.fr>

Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR),
Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 120923A detected by SWIFT
(trigger 534402) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 104.6s after the GRB trigger
(16.8s after the notice). The elevation of the field decreased
from 16 degrees above horizon and weather conditions
were good.

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 any OT at the XRT position (Yershov et al.
GCNC 13796) with a limiting magnitude of:

t0+105s to t0+165s : R > 16.0

We co-added a series of exposures:
t0+178s to t0+329s : R > 17.9

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

Note that there is NOMAD1 0962-0583888 (R.A.=303.7958222
Decl=+06.2200278 J2000) R=17.9 very close to the XRT position.
This source is detected on TAROT images but the sampling of
TAROT (3.3 arcsec/pixel) does not allow to separate an OT
from this star.

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