{
  "bibcode": "2002GCN..1645....1M",
  "body": "Malesani D., Stefanon M., Covino S., Ghisellini G. (INAF-OAB), Lazzati D., \nRossi E. (IOA, Cambridge, UK), Fugazza D., Guerra J.C., Pedani M. (INAF-TNG), \nMasetti N. (IASF-CNR), Pian E. (INAF-OATs), on behalf of a larger Italian \ncollaboration, report:\n\n\nOn Oct ~16.9 UT, we observed the optical counterpart of GRB 021004 (Shirasaki \net al., GCN 1565; Fox, GCN 1564) using the 3.6m TNG telescope in the Canary \nIslands; observations were performed with V (20 min), R (9 min) and I (15 \nmin) filters under mediocre conditions (seeing 1.5-1.8 arcsec, thin clouds). \nWith respect to the comparison star used by Fox and calibrated by Henden (GCN \n1583), the source has the following magnitudes:\n\n\nUT      Band  Mag    Error\n--------------------------\n16.979  I     21.65  0.12\n16.942  R     22.38  0.20\n16.962  V     22.49  0.07\n\n\nThe object is quite faint in our images. Actually, it lies about ~0.7 mag \nbelow the powerlaw extrapolation of the previously published data (R band), \nif we include the three early-time data points of Fox (t < 20 min). If \ninstead we let the powerlaw fit to begin ~2 hours after the trigger, there is \nno disagreement. A light curve with the relevant fits is reported at \nhttp://www.merate.mi.astro.it/~malesani/GRB/021004 .\n\n\nIf indeed a break has occured between Oct 10 and Oct 17 (6 to 13 days after \nGRB), this is in agreement with the prediction of GCN 1607.\n\n\nFurther observation are encouraged to assess the nature of this break.\n\n\nThis message may be cited.",
  "circularId": 1645,
  "createdOn": 1035022440000,
  "email": "covino@merate.mi.astro.it",
  "subject": "GRB 021004: VRI observations at TNG: possible break",
  "submitter": "Stefano Covino at Brera Astronomical Observatory  <covino@merate.mi.astro.it>",
  "eventId": "GRB 021004"
}