[vsnet-grb-info 12521] GRB 121024A: TAROT Calern observatory optical detection of a bright counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13887
SUBJECT: GRB 121024A: TAROT Calern observatory optical detection of a bright counterpart
DATE:    12/10/24 03:20:53 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 121024A detected by SWIFT
(trigger 536580) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 45.0s after the GRB trigger
(13.9s after the notice). The elevation of the field decreased from
32 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 detect a new fading source in the error box given by SWIFT
We detected the candidate couterpart mentioned by XXX et al. (GCNC XXXX)
at the following position (+/- 1 arcsec):

RA(J2000.0) = 04h 41m 53.41s
DEC(J2000.0) -12d 17' 26.9"

OT was R~13.3 betwenn 45.0s and 60s after GRB.
Then the flux decreases.

Observations are continuing.

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

N.B. Galactic coordinates are lon=209.4933 lat=-34.2488
and the galactic extinction in R band is about 0.1 magnitude
estimated from D. Schlegel et al. 1998ApJ...500..525S.

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