{
  "bibcode": "2007GCN..7097....1B",
  "body": "D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),\nG. Cusumano (INAF-IASFPA), C. Guidorzi (Univ Bicocca&INAF-OAB),\nS. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),\nH. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA),\nF. E. Marshall (NASA/GSFC), A. Moretti (INAF-OAB),\nP. T. O'Brien (U Leicester), D. M. Palmer (LANL),\nP. Romano (Univ. Bicocca & INAF-OAB), B. Sbarufatti (INAF-IASFPA),\nM. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),\nE. Troja (INAF-IASFPA), T. N. Ukwatta (GSFC/GWU) and\nD. E. Vanden Berk (PSU) report on behalf of the Swift Team:\n\nAt 17:40:37 UT, the Swift Burst Alert Telescope (BAT) found a source\nthat was not in its onboard catalog (trigger=296739) in a 320 second\nexposure.  Swift slewed automatically to the location about 7 minutes\nafter discovery. The BAT on-board calculated location is \nRA, Dec 104.555, -7.202 which is \n   RA(J2000) = 06h 58m 13s\n   Dec(J2000) = -07d 12' 07\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  This is consistent with the known source\nMXB 0656-072, which has recently been showing increased activity\n(ATELs #1281, #1283).  The TDRSS light curve shows no\nobvious variability, as is typical for long image triggers. \n\nThe XRT began observing the field at 17:53:55 UT, 798 seconds after the\nBAT trigger. XRT found a bright X-ray source\nlocated at RA, Dec 104.5711, -7.2086 which is\n   RA(J2000)  =  06h 58m 17.0s\n   Dec(J2000) = -07d 12' 30.9\"\nwith an uncertainty of 5.4 arcseconds (radius, 90% containment). \nWe cannot tell from initial quick-look data whether the source is fading. \nThis location is 62 arcseconds from the BAT on-board position,\nwithin the BAT error circle and 4.1 arcminutes from the Simbad position \nof MXB 0656-072. The initial flux in the 2.5s image was 1.2e-09 erg/cm2/s\n(0.2-10 keV). \n\nUVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)\nfilter starting 806 seconds after the BAT trigger. No afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers 100% of\nthe XRT error circle. The typical 3-sigma upper limit has been about 18.5 mag. \nThe 8'x8' region for the list of sources generated on-board covers 100% of the\nXRT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the extinction of E(B-V) = 1.247. \n\nThe Swift Narrow Field Instruments will continue to observe this\nsource for a couple of orbits before returning to the previous\nobserving schedule.",
  "circularId": 7097,
  "createdOn": 1195237120000,
  "email": "dxb15@psu.edu",
  "subject": "Swift detection of MXB 0656-072",
  "submitter": "David Burrows at PSU/Swift  <dxb15@psu.edu>"
}