{
  "bibcode": "2009GCN..9175....1H",
  "body": "S. T. Holland (CRESST/GSFC/USRA) and V. Mangano (INAF-IASFPA) report\non the behalf of the Swift UVOT team:\n\n        The Swift/UVOT observed the field of GRB 090418A starting 84 s\nafter the BAT trigger (Mangano, et al. 2009, GCN Circ. 9149).\nSettled exposures started at T+160 s.  The refined UVOT position for the\noptical afterglow is\n\n       RA (J2000) =  17:57:15.17  =  269.31321 (deg)\n      Dec (J2000) = +33:24:21.1   =  +33.40585 (deg)\n\nwith an estimated uncertainty of 0.5 arcsec (radius, 90% confidence,\nstatistical + systematic).  Preliminary 3-sigma magnitudes and upper\nlimits are\n\nFilter   T_start   T_stop   Exp(s)      Mag  Err\n-------------------------------------------------------------\nu (fc)       160      410      246    17.31 0.09\n\nv            466      485       19    17.31 0.24\nb            415      435       19    18.22 0.25\nu            539      559       19    18.55 0.39\nuvw1         515      835       19   >18.1        3-sigma UL\nuvm2         490      510       19   >17.6        3-sigma UL\nuvw2         441      461       19   >18.1        3-sigma UL\n\nuvw1         515   11,831     1337    20.82 0.26\n          114,115  131,895     2064   >22.0        3-sigma UL\nuvm2         490   18,413     2109   >21.8        3-sigma UL\nuvw2         441   16,709     1357   >21.8        3-sigma UL\n-------------------------------------------------------------\n\nThe quoted magnitudes have not been corrected for the expected\nGalactic extinction along the line of sight corresponding to a\nreddening of E_{B-V} = 0.04 mag (Schlegel, et al., 1998, ApJS, 500,\n525).  All photometry is on the UVOT flight system described in Poole\net al. (2008, MNRAS, 383, 627).\n\n      The detection in the uvw1 filter, combined with the lack of a\ndetection in the uvm2 filter, is consistent with this source having a\nredshift of z = 1.608 (Charnock, et al., 2009, GCN Circ. 9151).",
  "circularId": 9175,
  "createdOn": 1240256836000,
  "email": "Stephen.T.Holland@nasa.gov",
  "subject": "GRB 090418A: Swift/UVOT Observations",
  "submitter": "Stephen Holland at USRA/NASA/GSFC/SSC  <Stephen.T.Holland@nasa.gov>",
  "eventId": "GRB 090418A"
}