{
  "bibcode": "1999GCN...413....1P",
  "body": "Optical Observations of GRB990907\n\nE. Palazzi, E. Pian, N. Masetti, F. Frontera (ITESRE, CNR, Bologna), \nP.M. Vreeswijk, E. Rol (U. of Amsterdam), H. Pedersen, J. Hjorth (CUO,\nCopenhagen), J. van Paradijs (U. of Amsterdam and U. of Alabama in\nHuntsville), C. Kouveliotou (NASA-MSFC/USRA), P. Leisy, A. Pizzella, \nE. Pompei (ESO-La Silla), R. Mennickent (Univ. de Concepcion, Chile),\nC.G. Tinney, F. Freeman, S. Lee, J. Hawthorn (AAO), R. McMahon, S. Maddox,\nC. Singleton (IoA, Cambridge), and H. Jones (RSAA), on behalf of the\nBeppoSAX and Amsterdam/Huntsville GRB optical follow-up teams, report:\n\n\"We obtained V band images of the GRB 990907 field (GCN #405 and \nGCN #409) at the Anglo Australian Telescope with Taurus + MITLL2, \nat the ESO 1.54m Danish telescope with DFOSC, and at the ESO VLT telescope\nwith FORS1, beginning 24.9 hrs after the GRB event. Images in other bands \n(R and I) were also acquired as detailed in the following table: \n\n\n  Telescope   Date (UT)     Filter   Exptime    Limit mag.   Seeing\n\t\t\t\t\t\t(3-sigma)     \n\n    AAT      Sep  8.7698      V      480 sec      23.2        1\".4\n   Danish    Sep  9.3736      V     1600 sec      23.0        2\".6\n   Danish    Sep  9.3755      R     1600 sec      23.0        2\".6\n   Danish    Sep  9.3854      I     1600 sec      22.5        3\".5\n    AAT      Sep 10.7806      V      800 sec      22.7        2\".8\n    VLT      Sep 10.4111      V      180 sec      23.5        1\".1\n    VLT      Sep 10.4153      R      180 sec      23.6        1\".1\n    AAT      Sep 18.3736      V      960 sec      23.2        2\".2\n\n\nPhotometric calibration was done using standard stars in the Landolt\nfield PG0231+051. Comparisons were made among the V, R, and I band\nimages with the Digital Sky Survey, between the two R and among the \nfive V frames taken at different epochs.\nThe comparison does not show any object with significant brightness\nvariations larger than 0.3 mag.\n\n\nThis message can be cited.\"",
  "circularId": 413,
  "createdOn": 938090465000,
  "email": "masetti@tesre.bo.cnr.it",
  "subject": "Optical Observations of GRB990907",
  "submitter": "Nicola Masetti at ITeSRE,CNR,Bologna  <masetti@tesre.bo.cnr.it>",
  "eventId": "GRB 990907"
}