[vsnet-grb-info 15950] GRB 141225A: TAROT Calern observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17243
SUBJECT: GRB 141225A: TAROT Calern observatory optical observations
DATE:    14/12/27 00:45:35 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 141225A detected by SWIFT
(trigger 513505) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 8.2 min after the GRB trigger.
The elevation of the field increased from
50 degrees above horizon and weather conditions
were good.

We co-added a series of exposures to measure the optical
afterglow discovered by Gorosabel et al. (GCNC 17230):

Tstart Tend
(sec)  (sec) Rmag +/-
  496    907  18.8 0.3
  918   1315  19.0 0.3
1327   1728  19.9 0.5

The afterglow is no longer detected in the next images.

Magnitudes were estimated using USNO-B1 star USNO-B1 1237-0186662
(R.A.=138.789, Dec=+33.797) as Sonbas et al. (GCNC 17240).
Magnitudes are not corrected for galactic dust extinction.