{
  "bibcode": "2009GCN.10108....1M",
  "body": "F. E. Marshall (GSFC) and D. Grupe (PSU) report on  \nbehalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 091029\n91 sec. after the BAT trigger (Grupe et al., GCN Circ. 10097). \nWe detect the optical afterglow at the refined UVOT position\nRA, Dec 60.17745, -55.95557, which is\n\n     RA  (J2000)  04:00:42.59\n     Dec (J2000) -55:57:20.0\n\nwith an estimated uncertainty of 0.55 arcsec (radius, 90% confidence).\nThis position is consistent with the enhanced XRT position (Goad\net al., GCN 10102). The detection in the white, v, b and u filters and\nnot in the UV filters is consistent with the redshift\nof 2.752 (Chornock et al., GCN 10053).\n\nThe afterglow brightened by a factor of 4 between the first two\nobservations in the white filter, which had mean observing times\nof T+166 s. and T+594s. The afterglow then decayed following\nan approximately power law form with a decay index of -0.45.\nThis decay form lasted until at least T+8231 s.\nA similar optical light curve was reported by LaCluze et al.\n(GCN Circ. 10099 and 10107).\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        91        240       147          20.22 +/- 0.13\nwhite       584        603        19          18.75 +/- 0.14\nv           635        654        19          17.81 +/- 0.26\nb           559        578        19          19.04 +/- 0.28\nu           303        552        19          18.42 +/- 0.08\nuvw1        684       1280        58          > 19.32\nuvm2       1930       1949        19          > 18.74\nuvw2        611       1206        58          > 20.45\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": 10108,
  "createdOn": 1256850794000,
  "email": "marshall@milkyway.gsfc.nasa.gov",
  "subject": "GRB091029: Swift/UVOT observations",
  "submitter": "Frank Marshall at GSFC  <marshall@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 091029"
}