{
  "bibcode": "2005GCN..3089....1D",
  "body": "P. D'Avanzo, D. Fugazza, S. Covino (INAF-OABr), D. Malesani (SISSA), N. \nMasetti, E. Palazzi (IASF-CNR), L.A. Antonelli, G.L. Israel (INAF-OARm), \nand G. Andreuzzi (INAF-TNG), report on behalf of a larger Italian \ncollaboration:\n\nWe imaged again (Fugazza et al., GCN 3078) the field of GRB 050306 \n(Markwardt et al., GCN 3071) with the Italian TNG telescope. \nObservations were carried out under a clear sky and with a seeing of \nabout 1.6\", starting on 2005 Mar 9.247 UT. Seven R-band exposures were \nacquired, with an overall exposure time of 21 minutes (mean UT Mar \n9.260, i.e. 3.11 days after the burst).\n\nInside the revised error circle of the XRT afterglow (Perri et al., GCN \n3075; Mangano et al., GCN 3086), we detect several sources. After \nperforming PSF photometry with DAOPhot, we find that the object at \ncoordinates:\n\n  alpha(J2000) =  18:49:13.95\n  delta(J2000) = -09:09:08.6\n\n(that is, 3.5\" off the XRT centroid position) has faded by 0.54+-0.10 \nmag since our previous observation, carried out ~2.1 days after the GRB \n(Fugazza et al., GCN 3078). Assuming a powerlaw decay (F(t) = \nK*t^-delta), this corresponds to delta = 1.28+-0.24, a value typical \namong GRB afterglows at comparable epochs. We thus propose that this \nobject is the optical afterglow of GRB050603. Based on calibration upon \nUSNO stars, the object has R ~ 23 at the time of our first observation, \nMar 8.25 UT.\n\nA finding chart of the field is posted at the following URL:\nhttp://www.sissa.it/~malesani/GRB/050306\n\nFurther observations are planned at the TNG in the following nights, but \nno spectroscopy will be possible.\n\nWe warmly acknowledge the TNG staff for carefully performing the \nobservations.\n\nThis message can be cited.",
  "circularId": 3089,
  "createdOn": 1110653162000,
  "email": "malesani@sissa.it",
  "subject": "GRB 050306: optical afterglow",
  "submitter": "Daniele Malesani at SISSA-ISAS,Trieste,Italy  <malesani@sissa.it>",
  "eventId": "GRB 050306"
}