[vsnet-grb-info 17571] GRB 151215A: TAROT Calern observatory very early optical detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19001
SUBJECT: GRB 151215A: TAROT Calern observatory very early optical detection
DATE:    16/02/07 22:36:40 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz at free.fr>

Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:

We imaged the field of GRB 151215A detected by SWIFT
(trigger 667392) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 31.6s after the GRB trigger
(17.7s after the notice). The elevation of the field decreased
from 56 degrees above horizon and weather conditions
were good but images were slightly unfocused.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
Due to the unfocused condition, we took time to
reprocess the image to extract the magnitude of the
optical transient discovered by Cenko et al. (GCNC 18692):

t1(s) t2(s)  Rmag   d_Rmag
31.6  44.5  17.3    0.5
44.5  91.6  16.7    0.3

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