{
  "bibcode": "2009GCN.10054....1O",
  "body": "S. R. Oates (MSSL-UCL) and J. L. Racusin (NASA/GSFC/ORAU) report on  \nbehalf of the Swift/UVOT team:\n\nThe Swift/UVOT began observerving the field of GRB 091020 89 s\nafter the BAT trigger (Racusin et al., GCN Circ. 10048). We detect the\noptical afterglow in all filters at the refined UVOT position\nRA, Dec 175.730, +50.97833, which is\n\n     RA  (J2000)  11:42:55.20\n     Dec (J2000)  50:58:42.0\n\nwith an estimated uncertainty of 0.5 arcsec (radius, 90% confidence).\nThis position is consistent with the enhanced XRT position (Beardmore\net al., GCN 10050). The detection in the white, v, b and u filters and\nthe weak detection in the uvw1 filter is consistent with a redshift\nz~1.7, which is consistent with redshift reported by NOT (Xu, et al.,  \nGCN 10053).\n\nPreliminary magnitudes and 3 sigma upper limits are reported below.\n\nFilter    T_start(s) T_stop(s)  Exposure(s)   Mag  Err\n------------------------------------------------------------------------\nwhite       89        239        147          15.73 +/- 0.01\nwhite       874       1024       147          17.27 +/- 0.03\nv           799       819        19           16.40 +/- 0.15\nb           1153      1173       19           17.27 +/- 0.15\nu           707       727        19           17.06 +/- 0.16\nuvw1        683       6929       490          20.29 +/- 0.35\nuvm2        657       6723       490          > 20.29\nuvw2        608       6314       303          > 20.27\n-------------------------------------------------------------------------\n\nThe above magnitudes are not corrected for the Galactic extinction\ncorresponding to a reddening of E_{B-V} = 0.02 mag (Schlegel et al.,\n1998, ApJS, 500, 525).  The photometry is on the UVOT photometric system\ndescribed in Poole et al. (2008, MNRAS, 383,627).",
  "circularId": 10054,
  "createdOn": 1256123938000,
  "email": "sro@mssl.ucl.ac.uk",
  "subject": "GRB091020 Swift/UVOT observations",
  "submitter": "Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>",
  "eventId": "GRB 091020"
}