GCN Circular 1419

J. Gorosabel* (IAA-CSIC Granada), J. Hjorth, P. Jakobsson, J. Rasmussen, 
B. L. Jensen, H. Pedersen (Univ. of Copenhagen), J. M. Castro Ceron* 
(ROA San Fernando), A. Hornstrup (DSRI Copenhagen), A.O. Jaunsen (ESO Paranal),
M. Weidinger, J. Fynbo* (IFA Aarhus), M. I. Andersen (Univ. of Oulu),
P. Moller  (ESO Garching), S. Holland (Univ. of Notre Dame),
A. J. Castro-Tirado (IAA-CSIC Granada), E. Pian (INAF, OA Trieste),
A. Fruchter (STScI, Baltimore), J. Greiner (MPE Garching and AI Potsdam),
L. Kaper, E. van den Heuvel (Univ. of Amsterdam), on behalf of the GRACE 
collaboration, report:

We summarise the results of an optical and near-infrared search for the
afterglow of GRB 020418 carried out with the 1.54-m Danish Telescope and 
the 3.58-m New Technology Telescope, both at ESO's La Silla observatory.

The log of the observations is displayed in the following table:

 =========================================================================
       Date UT       Filter ExpTime Telescope   Seeing Time since Error box
       2002                   (s)  (+Instrument) (")   GRB (days) Coverage (%)
 --------------------------------------------------------------------------
 April 19.9435--20.0066 Ks  45x60 3.58NTT(+SOFI) 0.65    1.6150    60**
 April 19.9445--19.9935 J   20x60 3.58NTT(+SOFI) 0.65    1.6089    60**
 April 19.9760--20.0507 R  10x420 1.54D(+DFOSC)  1.05    1.6532    100
 April 20.9541--21.0177 Ks  45x60 3.58NTT(+SOFI) 0.70    2.6258    60**
 April 20.9551--21.0052 J   20x60 3.58NTT(+SOFI) 0.70    2.6200    60**
 April 20.9720--21.0340 R   6x500 1.54D(+DFOSC)  0.90    2.6429    100
 June  01.9642--02.0267 R   9x500 1.54D(+DFOSC)  1.90   44.6353    100
 June  02.9592--03.0155 R   8x500 1.54D(+DFOSC)  1.40   45.6273    100
 --------------------------------------------------------------------------
 ** Central part
 ==========================================================================

Comparison of the images reveals no variable source contained in the error
box brighter than R = 23.0. Correcting for the effect of the Galactic 
extinction, the R-band upper limit corresponds to R = 22.3. 

For the central part of the error box (the 60% of the error box covered for 
SOFI) we can set limits of Ks >= 21.0, J >= 22.6 and R >= 22.3 for any 
variable source (magnitudes corrected for Galactic reddening).

We acknowledge the assistance of L. Vanzi at La Silla.

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* Visiting the Astronomical Observatory of the University of Copenhagen.