[vsnet-grb-info 5893] GRB 080330: TAROT Calern observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7543
SUBJECT: GRB 080330: TAROT Calern observatory optical observations
DATE:    08/03/30 06:31:40 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 complete the TAROT analysis of GRB 080330 detected by SWIFT
(trigger 308041) at the location of the rising afterglow
detected by Klotz et al. (GCNC 7536). We refined the
coordinates (better than 1 arcsec) :

RA(J2000.0) = 11h 17m 04s49
DEC(J2000.0) +30d 37' 23"5

We consider the date of trigger : t0 = 2008-03-30T03:41:17

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect the OT with a limiting magnitude of:
t0+20.4s to t0+80.4s : R > 17.0

This limiting magnitude is compatible with the detection
R~17.5 by ROTSE-IIIb (Schaefer et Guver GCNC 7538) at
~t0+25s.

The later images, in tracking mode, show the afterglow.
We measured the alpha index considering flat flux is
proportional to t^-alpha:

t0+ 88s to t0+ 332s : alpha=-0.8 (rise)
t0+332s to t0+ 428s : maximum of brightness R~16.8
t0+428s to t0+1068s : alpha=+0.4 (decay)
t0+1068s : R~17.2

Two images were taken between t0+1177s
and t0+1363s during the dawn. They seem to show
a plateau or even a rebrightening.
Observations are now stoped at Calern.

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