{
  "circularId": 43529,
  "subject": "GRB 260127A: Swift detection of a burst",
  "createdOn": 1769537839276,
  "submitter": "K.L. Page at U Leicester <klp5@leicester.ac.uk>",
  "body": "N. J. Klingler (GSFC/UMBC/CRESSTII), R. Gupta (NASA GSFC),\nJ. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),\nK. L. Page (U Leicester), T. M. Parsotan (GSFC) and\nB. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 17:50:34 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 260127A (trigger=1444088).  Swift slewed immediately to the burst.\nThe BAT on-board calculated location is \nRA, Dec 231.857, +6.758 which is \n   RA(J2000) = 15h 27m 26s\n   Dec(J2000) = +06d 45' 30\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed no\nstructure initially, typical of an image trigger, with a more \nclassic pulse structure starting at ~T0+20 sec. The emission \nhas a duration of about 50 sec.  The peak count rate was ~1460 \ncounts/sec (15-350 keV), at ~33 sec after the trigger.\n\nThe XRT began observing the field at 17:54:00.1 UT, 205.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source located at RA, Dec 231.87885, 6.76345\nwhich is equivalent to:\n   RA(J2000)  = 15h 27m 30.92s\n   Dec(J2000) = +06d 45' 48.4\"\nwith an uncertainty of 3.5 arcseconds (radius, 90% containment). This\nlocation is 80 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position may be improved as more data are received;\nthe latest position is available at https://www.swift.ac.uk/sper. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (4.07 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2\n(+2.30/-2.03) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 4.58e-10 erg cm^-2 s^-1 (0.2-10\nkeV).\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 213 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers none of\nthe XRT error circle. The 8'x8' region for the list of sources generated\non-board covers 100% of the XRT error circle. The list of sources is typically\ncomplete to about 18 mag. No correction has been made for the expected\nextinction corresponding to E(B-V) of 0.049.\n\nBurst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu).\nPlease contact the BA by email if you require additional information\nregarding Swift followup of this burst. In extremely urgent cases, after\ntrying the Burst Advocate, you can contact the Swift PI by phone (see\nSwift TOO web site for information: http://www.swift.psu.edu/)\n\n",
  "eventId": "GRB 260127A",
  "bibcode": "2026GCN.43529....1K",
  "submittedHow": "email"
}