GCN Circular 7311
Subject
GRB 080212: VLT optical rapid decay
Date
2008-02-14T19:37:21Z (16 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D'Avanzo, D. Fugazza (INAF-OAB), L.A. Antonelli (INAF-OAR), S.
Covino, G. Chincarini, C. Guidorzi, G. Tagliaferri (INAF-OAB), V.
D'Elia, F. Fiore, S. Piranomonte, L. Stella (INAF-OAR), M. Della Valle
(INAF-OAA), S. D. Vergani (DIAS-DCU) report on behalf of the MISTICI
collaboration:
We observed the optical afterglow of GRB 080212 (Ziaeepour et al., GCN
7296) with the ESO-VLT equipped with the FORS2 camera in imaging mode at
three different epochs. Observations have been carried out in R-band on
Feb 13.3101 UT, Feb 13.3682 UT and Feb 14.2838 UT (0.58, 0.64 and 1.55
days after the burst, respectively).
We found that between the first two epochs the afterglow faded very
rapidly, with a decay index of alpha ~ 5.5. Very likely, the afterglow
underwent a remarkable increase of its optical/NIR flux, probably
related to the brightening observed in the X-rays about 4 hours before
our VLT observations (see D'Avanzo et al., GCN 7310).
Assuming the above decay index, we estimate R ~ 20.8 at the epoch of the
REM detection (D'Avanzo et al., GCN 7302) with an implied colour R-H~5
The decay of the afterglow then slowed down between the last two epochs
and we measure R~25 in our last observation.