{
  "bibcode": "2021GCN.30222....1E",
  "body": "P. A. Evans (U Leicester), J. A. Kennea (PSU), N. J. Klingler (PSU),\nA. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and\nM. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 13:01:32 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated 4U 1543-47 (trigger=1055000).  This was a 19.1 minute long image\ntrigger, after which Swift slewed immediately to the source. \nThe BAT on-board calculated location is \nRA, Dec 236.772, -47.682 which is \n   RA(J2000) = 15h 47m 05s\n   Dec(J2000) = -47d 40' 55\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  No light curve near the trigger time\nis available at this moment. We are waiting for ground data for more information. \n\nThe XRT began observing the field at 13:23:51.8 UT, 1339.0 seconds\nafter the BAT trigger. XRT found a bright X-ray source located at RA,\nDec 236.7907, -47.6693 which is equivalent to:\n   RA(J2000)  = 15h 47m 9.77s\n   Dec(J2000) = -47d 40' 09.5\"\nwith an uncertainty of 10 arcseconds (radius, 90% containment). This\nlocation is 64 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position is 11.8\" from the position of 4U 1543-47 (ATel #98). \nAssuming a typical GRB power-law spectrum (NH=3e21 cm^-2, gamma=2), the\ncatalogue entry for this object  is equivalent to a 0.2-10 keV flux of\n1.4e-11 erg cm^-2 s^-1; the flux in the 0.1 s XRT image was 1.88e-07\nerg cm^-2 s^-1. No event data are yet available to determine the column\ndensity using X-ray spectroscopy. \n\nUVOT took a finding chart exposure of 150 seconds with the White\nfilter  starting 1347 seconds after the BAT trigger. The 2.7'x2.7'\nsub-image shows the 4U 1543-47 source with a white magnitude of 13.86\nand strong coincidence loss.  No correction has been made for\nextinction. \n\nThe position of the BAT and XRT sources are consistent with that of\nthe High-Mass X-ray Binary 4U 1543-47 (Atel #98), thus we believe this\nto be an outburst of that source.",
  "circularId": 30222,
  "createdOn": 1623506303000,
  "email": "pae9@star.le.ac.uk",
  "subject": "Swift-BAT Trigger 1055000: Swift detection of an outburst from 4U 1543-47",
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>"
}