{
  "submitter": "K.L. Page at U Leicester <klp5@leicester.ac.uk>",
  "bibcode": "2026GCN.43442....1G",
  "body": "R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL),\nK. L. Page (U Leicester) and T. Sakamoto (AGU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 11:27:54 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated the HMXB 1A 1118-61 (trigger 1442056).  Swift slewed immediately \nto the source. The BAT on-board calculated location is \nRA, Dec 170.230, -61.909 which is \n   RA(J2000) = 11h 20m 55s\n   Dec(J2000) = -61d 54' 32\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty). As is usual for an image trigger, the \nlight-curve does not show significant structure.\n\nThe XRT began observing the field at 11:29:57.7 UT, 122.8 seconds after\nthe BAT trigger. XRT found a bright X-ray source located at RA, Dec\n170.2386, -61.9161 which is equivalent to:\n   RA(J2000)  = 11h 20m 57.26s\n   Dec(J2000) = -61d 54' 58.0\"\nwith an uncertainty of 5.1 arcseconds (radius, 90% containment). This\nlocation is 29 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position is 1.8 arcseconds from a known X-ray\nsource: 1A 1118-61. This source is in the Swift XRT LSXPS \ncatalogue with a mean 0.3-10 keV count-rate of 0.2537 +/- 0.0012\nct/sec; see https://www.swift.ac.uk/LSXPS/LSXPS%20J112057.1-615459 for\ndetails of these previous observations. No event data are yet available\nto determine the column density using X-ray spectroscopy.\n\nUVOT took a finding chart exposure of 250 seconds with the U filter\nstarting  188 seconds after the BAT trigger. The source is clearly\ndetected at a U magnitude of 12.7. No correction has been made for the\nlarge, but uncertain, extinction expected.\n\nThis is the second recent trigger by Swift-BAT on this source,\nfollowing yesterday's event reported in GCN Circ. 43435, showing that\nthe source is increasing in brightness.\n\n",
  "createdOn": 1768737429501,
  "subject": "Swift trigger on the HMXB 1A 1118-61",
  "submittedHow": "email",
  "circularId": 43442
}