GCN Circular 7108

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 071117 detected by SWIFT
(trigger 296805) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 9.5h after the GRB trigger
(GRB occured during daytime). The elevation of the field
decreased from from 54 degrees above horizon and weather
conditions were excellents.

We co-added series of exposures taken in VRI filters
from t_trig+9.5h to t_trig+11.3h. There is no OT detected in
V and R bands. A source is detected in the I-band
close to the limiting magnitude I~20 at a position
compatible with XRT (Romano et al. GCNC 7100) and
s1,s2 sources of Bloom (GCNC 7105). Due to the spatial
sampling of TAROT (3.3arcsec/pixel) and to the very low
signal to noise ratio we cannot discriminate
between s1 and s2.

The source is also present in I-band in series
11.6-13.3 h and also in the series 13.7-15.8 h but
the actual processing does not allow to say if the
brightness decreases or not.

If we consider the I-band source TAROT is the same as the
s1 source of Bloom (R=23.3), the corresponding (R-I)~3
is very high. The galactic extinction in R band is only 0.06
magnitude (estimated from D. Schlegel et al. 1998).
As a consequence, we estimate that GRB 071117 is a good
high redshift candidate (z>4.5).

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