[AAVSO-HEN] GRB 090205: VLT optical decay

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TITLE:   GCN CIRCULAR
NUMBER:  8895
SUBJECT: GRB 090205: VLT optical decay
DATE:    09/02/07 09:35:05 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <paolo.davanzo at brera.inaf.it>

P. D'Avanzo, D. Fugazza (INAF-OAB), V. D'Elia (INAF-OAR), R. Salvaterra, 
C. C. Thoene (INAF-OAB), S.  Piranomonte (INAF-OAR), S. Covino, S. 
Campana (INAF-OAB), G. Chincarini (Univ. Bicocca) report, on behalf of 
the MISTICI collaboration:

We continued monitoring GRB 090205 (Perri et al., GCN 8884) with the 
ESO-VLT in imaging mode. Observations were carried out in R-band with 
the FORS1 camera about 1.35 days after the burst.

Preliminary analysis of a first set of images (total exposure: 12 min) 
reveals that the optical afterglow (D'Avanzo et al. GCN 8887; Kruehler & 
Greiner GCN 8888) is still detected and that it faded by about 3 mags 
with respect to our previous epoch of VLT observations (D'Avanzo et al. 
GCN 8887). Assuming a power-law decy, the inferred decay index between 
this two epochs is alpha ~ 1.8, steeper than what measured in the X-rays 
at earlier epochs (Perri & Stratta, GCN 8891). Further optical 
observations are ongoing.


We acknowledge the VLT staff for their support, in particular G. James 
and L. Schmidtobreick.