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GCN Circular 2651

Subject
XRF 040812: optical observation at VLT
Date
2004-08-18T20:19:37Z (20 years ago)
From
Daniele Malesani at SISSA-ISAS,Trieste,Italy <malesani@sissa.it>
P. D'Avanzo, A. Cucchiara, G. Tagliaferri, D. Malesani, D. Fugazza, S. 
Covino, S. Campana, on behalf of a larger collaboration, report

We observed the field of XRF 040812 (Gotz et al. GCN 2640) with the 
ESO-VLT on Aug 12.9795 UT (~17.5 hours after the GRB) and Aug 13.9844 UT 
(~41.5 hours after the GRB). Observations were performed in the I-band, 
under good observing conditions.
Ten 1-minute exposures were taken in both nights. The seeing was 1.1" on 
Aug 12 and 0.8" on Aug 13. We estimate the limiting magnitude to be I ~ 24.
To avoid saturation from the bright star close to the center of the field, 
we had to place on occulting bar, which hides 9% of the error box.

We briefly report about the Chandra X-ray sources (Patel et al. GCN 1648).

Source #1, #3 and #7 are visible in the DSS, as well as in our images.
Source #2 (see also Campana & Moretti, GCN 1649) is not detected in the 
DSS and, moreover, in our images it is falling just behind the occulting 
bar.
Source #4 is close (~1.5"), but not coincident, with a faint source in the 
VLT images, not visible in the DSS.
Source #5, #6 are visible in our images but not in the DSS.

None of the counterparts of the Chandra sources shows any significant 
variability. Moreover we don't have evidence of candidates in the whole 
Integral error-box (Gotz et al. GCN 2640), in particular at the radio 
position (Soderberg GCN 2643).

PSF-matched photometry was performed with DAOPHOT and image subtraction 
with ISIS.

We thank the ESO staff at Paranal for carefully performing the 
observations.

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