TITLE:   GCN CIRCULAR
NUMBER:  5943
SUBJECT: GRB 061218: TAROT La Silla observatory optical observations
DATE:    06/12/19 22:54:35 GMT
FROM:    Alain Klotz at CESR-CNRS  <Alain.Klotz@free.fr>

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

We imaged the field of GRB 061218 detected by SWIFT
(trigger 251863) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 126.5s after the GRB trigger
(69.6s after the notice). The elevation of the field increased from
from 30 degrees above horizon and weather conditions
were good.

The date of trigger : t0 = 2006-12-18T04:05:06.144

A technichal problem prevent to obtain a 60s image
at t0+58s. Moreover, images are slightly defocussed.

We examined the BAT position provided by
Sato et al. 2006 (GCN Circ. 5940).

The first image is 30.0s exposure in tracking mode:
We do not detect any OT with a limiting magnitude of:
t0+126.5s to t0+156.5s : R > 17.4

The second image is 30.0s exposure:
t0+162.3s to t0+192.3s : R > 17.4

We co-added a series of exposures:
t0+126.5s to t0+510.6s : R > 18.0

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

N.B. Galactic coordinates are lon=267.1250 lat=+15.3187
and the galactic extinction in R band is 0.3 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

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