[vsnet-grb-info 4176] GRB 061222B: TAROT La Silla observatory early optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5981
SUBJECT: GRB 061222B: TAROT La Silla observatory early optical observations
DATE:    06/12/25 01:48:01 GMT
FROM:    Alain Klotz at CESR-CNRS  <Alain.Klotz at free.fr>

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

We solve technichal problems that prevent to
acces to the first trailed image of GRB 061222B
obtained with TAROT located at the European Southern
Observatory, La Silla observatory, Chile.

The observations started 84.1s after the GRB trigger
(4s after the notice). The trailed image allows to
follow continuously variable source during the 60s
integration time (see technichal description in
Klotz et al., 2006, A&A 451, L39). The GRB expected
trail is blended with the trail of the USNO-B1 star
0641-0103259 of R=14.7 after 24s. During the 24 first
seconds we do not detect the optical transient brighter
than R~17.7. Moreover, we confirm the optical detection
in the first non trailed image (Klotz et al. GCN Circ.
5960) taken in the range t0+150 to t0+180s.
To summarize:

t0+ 84s to t0+108s : R > 17.7
t0+108s to t0+144s : R > 14.7
t0+150s to t0+180s : R = 18.2 +/- 0.5 (GCNC 5960)
t0+185s to t0+215s : R > 18.2
t0+150s to t0+534s : R = 19.9 (GCNC 5959)

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

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