TITLE:   GCN CIRCULAR
NUMBER:  7897
SUBJECT: GRB 080623: TAROT La Silla observatory optical observations
DATE:    08/06/23 12:26:04 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 080623 detected by SWIFT
(trigger 315080) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 425.1s after the GRB trigger
(14.8s after the notice). The elevation of the field
decreased from 12 degrees above horizon and weather
conditions were good but only four images of 90s were
taken due to the end of the night.

The date of trigger : t0 = 2008-06-23T10:25:28.44

We do not detect any optical transient
at the XRT position (Ukwatta et al. GCNC 7894)
with the following limiting magnitudes:

The first image is 90.0s exposure:
t0+425s to t0+515s : R > 16.2

We co-added the four exposures:
t0+425s to t0+802.0s : R > 17.0

This last value is conservative because
the star density is high and the spatial
sampling of TAROT (i.e. 3.3 arcsec/pix) is not
adapted to separate close sources fainter than
mag 17.0 at the XRT position.

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

N.B. Galactic coordinates are lon=322.3398 lat= -6.1221
and the galactic extinction in R band is 0.94 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

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