GCN Circular 449

Optical Observations of GRB991105

E. Palazzi, E. Pian, N. Masetti, F. Frontera (ITESRE, CNR, Bologna), 
E. Rol, P.M. Vreeswijk (U. of Amsterdam), P. McCarthy, H.-W. Chen, 
B. Schommer, C. Smith, N. Suntzeff (CTIO), H. Pedersen, J. Hjorth (CUO,
Copenhagen), C. Kouveliotou (NASA-MSFC/USRA), T. Augusteijn, and 
R. Athreya (ESO) on behalf of the BeppoSAX and Amsterdam/Huntsville GRB
optical follow-up teams, report: 

"We have observed the revised BeppoSAX WFC error circle of GRB 991105
(Piro 1999, GCN 433
Not found
 
 
) in the BRi bands at the ESO 2.2m telescope at La
Silla (Chile) 15.8 and 39.9 hours after the burst. 
  
The field is very crowded as it lies on the Galactic plane. The reddening
towards that direction is E(B-V) = 0.623 (Schlegel et al. 1998, ApJ 500,
525), implying a Galactic extinction of 2.7, 1.7 and 1.2 mag in B,R, and
i, respectively. No galaxies are seen in the field, which is also
indicative of considerable optical extinction.

Photometric calibration was done using standard stars in the Landolt
field SA98 (Landolt 1992, AJ 104, 340). The comparison between the two
sets of images does not show any object with significant brightness
variations larger than 0.5 mag down to the 3 sigma limiting magnitudes of
R=23.5, B=22.5, i=22.0.

We also observed the GRB field with the 4m telescope at CTIO (Chile),
taking images in the R band over 4 nights starting 15 hours after the
burst. SN search software has been applied to those images by N. Suntzeff
and collaborators. No variables were detected in the field down to a 3
sigma limiting magnitude R=23.4, thus confirming the results from the ESO
observations."


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