{
  "bibcode": "1999GCN...327....1M",
  "body": "N. Masetti, E. Palazzi, E. Pian, F. Frontera (ITESRE, CNR, Bologna),\nP.M. Vreeswijk, E. Rol, T.J. Galama (U. of Amsterdam), M. Della Valle \n(U. of Padua), E. Costa, M. Feroci, L. Piro (IAS, CNR, Rome), \nJ. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville), \nC. Kouveliotou (NASA-MSFC/USRA), O. Hainaut, A. Pizzella (ESO-La Silla),\nand D. Koester (Institut fuer Astronomie und Astrophysik, Kiel), \non behalf of the BeppoSAX and Amsterdam/Huntsville GRB optical\nfollow-up teams, report:\n\n\"Images of the GRB 990506 refined error box (Hurley et al., GCN #298) \nwere acquired with start times 1999 May 7.09, 7.26, 8.04, 9.98 and 10.00\nUT (exposure times are reported below) at ESO-La Silla with the 2.2m\ntelescope plus WFI.  \nZero-point R calibration was determined using the photometry by Vrba et\nal. (GCN #305) with an accuracy of 0.07 mag.\n\nComparison between the 15-min images of May 7.09 and 8.04 shows no object\nvarying by more than 0.3 magnitudes (3-sigma) down to R~22.6 within the\nGRB error box.\nIn order to reach a deeper magnitude limit, we summed the images of May 7\n(total limiting magnitude: R~24.0) and compared them with that of May 9\nand with that of May 10. In this case no object varying by more than 0.3\nmagnitudes down to R~23.0 is present inside the error box. \nIn all cases, no clearly variable object was seen within the IPN error box\ndown to the detection limits of the frames.\n\nLimiting magnitudes for the five epochs cited above are reported in the\nfollowing table:\n\n\n     Start time (UT)    Exp. time     R mag\n    ----------------------------------------\n     1999 May 07.09      15 min.      23.8\n     1999 May 07.26      15 min.      23.0\n     1999 May 08.04      15 min.      23.6\n     1999 May 09.98      30 min.      24.3\n     1999 May 10.00      30 min.      24.3\n\n\n\nThis message can be cited.\"",
  "circularId": 327,
  "createdOn": 926693861000,
  "email": "masetti@tesre.bo.cnr.it",
  "subject": "GRB 990506 R band observations",
  "submitter": "Nicola Masetti at ITeSRE,CNR,Bologna  <masetti@tesre.bo.cnr.it>",
  "eventId": "GRB 990506"
}