[vsnet-grb-info 54] VLT observations of GRB 020124: The fading optical/near-infrared afterglow

[GCN Circulars <gcncirc@lheawww.gsfc.nasa.gov>]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1227
SUBJECT: VLT observations of GRB 020124: The fading optical/near-infrared afterglow
DATE:    02/01/27 12:30:28 GMT
FROM:    Jens Hjorth at U.Copenhagen  <jens@astro.ku.dk>

VLT observations of GRB 020124: The fading optical/near-infrared afterglow


J. Hjorth (U. Copenhagen), J. Gorosabel (DSRI, Copenhagen), and J. Fynbo (ESO) 
report on behalf of the Gamma-Ray Afterglow Collaboration at ESO (GRACE):

We have obtained optical and near-infrared images of the possible optical 
afterglow (Price et al., GCN #1221; Gorosabel et al., GCN #1224; Bloom, GCN 
#1225) of GRB 020124 (Ricker et al., GCN #1220) with ESO's VLT. 30-min Ks-band
exposures were obtained with ISAAC/Antu on Jan 26.20 (seeing FWHM = 0.50") and 
Jan 27.20 (FWHM = 0.44") 2002 UT; a 15-min R-band image (FWHM = 0.66") was 
obtained with FORS1/Melipal on Jan 27.28 2002 UT. The source identified by 
Gorosabel et al. in NOT R-band images obtained on Jan 26.06 (cf. GCN #1224) 
has clearly faded in the FORS1 R-band image. The source is also detected in 
the ISAAC Ks data and is fading between the two epochs of observation. These 
findings strongly suggest that the source identified by Price et al. is indeed 
the optical/NIR afterglow of GRB 020124. A more detailed analysis of the data 
is in progress. Meanwhile, we have posted images showing the decaying Ks-band 
source at http://www.astro.ku.dk/~jens/GRB020124_ISAAC_Ks_GRACE.gif

We appreciate the kind and efficient assistance of the ESO staff at 
Paranal Observatory (Nancy Ageorges, Thomas Szeifert and Riccardo Scarpa) 
in conducting the reported service mode observations.

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