[vsnet-grb-info 2570] GRB 051227: refined analysis of VLT images

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4407
SUBJECT: GRB 051227: refined analysis of VLT images
DATE:    05/12/28 09:49:46 GMT
FROM:    Daniele Malesani at SISSA-ISAS,Trieste,Italy  <malesani at sissa.it>

D. Malesani (SISSA), S. Piranomonte, L.A. Antonelli (INAF/OARm), S. 
Campana (INAF/OABr), G. Chincarini (Univ. Milano-Bicocca), and L. Stella 
(INAF/OARm), report on behalf of the MISTICI collaboration:

The field of GRB 051227 (Barbier et al., GCN 4397; Barthelmy et al., GCN 
4401; Sakamoto et al., GCN 4403) was observed at two epochs with the 
ESO-VLT UT2, equipped with FORS1. Exposure was 20 minutes per epoch, 
with mean times 10.4 and 12.5 h after the GRB trigger.

Coaddition of all images confirms the presence of a single, faint source 
(Malesani et al., GCN 4404) at the edge of the revised XRT error circle 
(Beardmore et al., GCN 4402). A finding chart is posted at the following 
link:

http://www.sissa.it/~malesani/GRB/051227/GRB051227_finder.jpg

The source inside the XRT error circle (S1) shows a marginal dimming in 
the R band between the two epochs, by 0.34 +- 0.20 mag. The error was 
estimated by looking at the variations of several objects with 
brightness comparable to that of S1. We note that the seeing slightly 
worsened between the two epochs, passing from 1.3" to 1.6".