{
  "bibcode": "2010GCN.10703....1B",
  "body": "A. Breeveld (MSSL/UCL), A. Rowlinson, N. Lyons and R.L.C. Starling (U. \nLeicester) report on behalf of the Swift/UVOT team:\n\nSwift began settled observations of the field of GRB 100427A 110220 s \nafter the BAT rate increase detected in ground analysis (Cummings et \nal., GCN Circ. 10699). No afterglow consistent with the BAT position \ngiven in GCN Circ. 10699 is detected in the initial XRT or UVOT exposures.\n\nSwift-XRT obtained 5.9 ks of Photon Counting (PC) mode data, from T0 + \n110 ks to T0 + 144 ks. No source is found in the BAT error circle, \nwith a 3-sigma upper limit of 1.3 x 10-3 count s-1. For a typical GRB, \nthis would correspond to an upper limit on the 0.3 - 10 keV flux of 5 \nx 10-14 erg cm-2 s-1.\n\nFor the UVOT a preliminary 3-sigma upper limit for the initial summed \nexposures, using the UVOT photometric system (Poole et al. 2008, \nMNRAS, 383, 627),  is:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\nu               110220       143784         5836         >21.2\n\nThe values quoted above are not corrected for the Galactic extinction \ndue to the reddening of E(B-V) = 0.69 in the direction of the burst \n(Schlegel et al. 1998).",
  "circularId": 10703,
  "createdOn": 1272544920000,
  "email": "aab@mssl.ucl.ac.uk",
  "subject": "GRB 100427A: Swift XRT and UVOT Upper Limits",
  "submitter": "Alice Breeveld at MSSL-UCL  <aab@mssl.ucl.ac.uk>",
  "eventId": "GRB 100427A"
}