{
  "circularId": 37397,
  "submittedHow": "email",
  "bibcode": "2024GCN.37397....1D",
  "createdOn": 1725561968299,
  "subject": "GRB 240905E: Swift detection of a burst",
  "eventId": "GRB 240905E",
  "submitter": "Tyler Parsotan  at NASA GSFC <tyler.parsotan@nasa.gov>",
  "body": "S. Dichiara (PSU), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC),\nJ. A. Kennea (PSU), K. L. Page (U Leicester), T. M. Parsotan (GSFC)\nand M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 18:26:03 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 240905E (trigger=1252695).  Swift slewed immediately to the burst.\nThe BAT on-board calculated location is \nRA, Dec 345.799, +35.495 which is \n   RA(J2000) = 23h 03m 12s\n   Dec(J2000) = +35d 29' 42\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex double-peaked\nstructure with a duration of about 10 sec.  The peak count rate\nwas ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger.\n\nThe XRT began observing the field at 18:27:50.0 UT, 106.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright X-ray\nsource located at RA, Dec 345.80347, 35.52378 which is equivalent to:\n   RA(J2000)  = 23h 03m 12.83s\n   Dec(J2000) = +35d 31' 25.6\"\nwith an uncertainty of 4.3 arcseconds (radius, 90% containment). This\nlocation is 104 arcseconds from the BAT onboard position, within the\nBAT error circle. This position may be improved as more data are\nreceived; the latest position is available at\nhttps://www.swift.ac.uk/sper.  We cannot determine whether the source\nis fading at the present time. This position is 22.7 arcseconds from\nthat of a known X-ray source: 1RXS J230313.6+353105 in the ROSAT\nRASSFSC catalogue. Assuming a typical GRB power-law spectrum (NH=3e21\ncm^-2, gamma=2), the catalogue entry for this object  is equivalent to\na 0.2-10 keV flux of 1.4e-12 erg cm^-2 s^-1; the flux in the 2.5 s XRT\nimage was 1.11e-09 erg cm^-2 s^-1. No spectrum from the promptly\ndownlinked event data is yet available to determine the column density.\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 115 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 0.076.\n\nWe note that the X-ray source is near to a catalogued X-ray source, 1RXS \nJ230313.6+353105. However, this is not a known transient source, and is likely a \nchance coincidence. Therefore at this time, we believe that this is a GRB.\n\nBurst Advocate for this burst is S. Dichiara (sbd5667 AT psu.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"
}