{
  "bibcode": "2009GCN..9877....1S",
  "body": "C. A. Swenson (PSU) and G. Stratta (ASDC) report on behalf of the\nSwift/UVOT team:\n\nThe Swift/UVOT began observations of the field of GRB 090902B\napproximately 12.5 hours after the Fermi GBM/LAT trigger (de Palma\net al., GCN Circ. 9867; Bissaldi et al., GCN Circ. 9866).  We can\nnow confirm the detection of the optical afterglow (Swenson et al.,\nGCN Circ. 9869; Perley et al., GCN Circ. 9870; Cucchiara et al.,\nGCN Circ. 9873; Olivares et al., GCN Circ. 9874; Guidorzi et al.,\nGCN Circ. 9875) coincident with the enhanced Swift-XRT position (Evans,\nGCN Circ. 9871).  We also observe a decay in the optical afterglow.\n\nThe observed magnitudes using the UVOT photometric system (Poole et\nal. 2008, MNRAS, 383, 627) are:\n\nFilter       T_start(s)     T_stop(s)      Exp(s)         Mag\n\nu              45096          46188         1075        20.26 � 0.19\nu              50891          58703         3613        20.50 � 0.11\nu              62457          81106         8756        20.85 � 0.10\n\nThe values quoted above are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.04 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 9877,
  "createdOn": 1252007745000,
  "email": "cswenson@astro.psu.edu",
  "subject": "GRB 090902B:  Swift/UVOT refined analysis",
  "submitter": "Craig Swenson at PSU/Swift  <cswenson@astro.psu.edu>",
  "eventId": "GRB 090902B"
}