[vsnet-grb-info 4087] GRB 061201: VLT optical decay

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5896
SUBJECT: GRB 061201: VLT optical decay
DATE:    06/12/03 22:58:20 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <paolo.davanzo at brera.inaf.it>

P. D'Avanzo (INAF-OABr & Univ. Insubria) and S. Piranomonte (INAF-OAR) 
report on behalf of the MISTICI collaboration:

We continued monitoring the afterglow of the short GRB061201 (Marshall 
et al., GCN 5881) with the VLT equipped with the FORS2 camera. 
Observations were carried out in the I filter. From a comparison with a 
set of nearby field stars we conclude that the object detected in our 
previous images (D'Avanzo et al. GCN 5884; see also Holland et al. GCN 
5883) faded in the I-band by about 1.8 mag between Dec 2.025 UT and Dec 
3.045 UT (0.359 and 1.379 days after the burst, respectively). The 
inferred decay index is thus ~ 1.2.

We note a discrepancy of about 0.7 mag in the absolute calibration 
during the two nights, based on observations of Landolt standard fields. 
We thus warn that the absolute calibration is still preliminary. The 
decay slope is however independent of this and thus robust.

We thus fully confirm that the object proposed by  Holland et al. (GCN 
5883) and D'Avanzo et al. (GCN 5884), as already found by Haislip et al. 
(GCN 5895).

We thank the support of the ESO staff.

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