{
  "createdOn": 1713530616084,
  "bibcode": "2024GCN.36180....1D",
  "circularId": 36180,
  "subject": "GRB 240419B: Swift detection of a burst",
  "submittedHow": "email",
  "body": "\nS. Dichiara (PSU), J.D. Gropp (PSU), R. Gupta (NASA/GSFC),\nF. E. Marshall (NASA/GSFC), M. J. Moss (GSFC),\nP. T. O'Brien (U Leicester), M. H. Siegel (PSU) and\nM. A. Williams (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 12:22:52 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 240419B (trigger=1223072).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 325.877, +4.234 which is \n   RA(J2000) = 21h 43m 30s\n   Dec(J2000) = +04d 14' 01\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex structure lasted \nfor ~40 seconds and returned to background before showing three bright pulses at \n~100 seconds for a total duration of 160 seconds.  The peak count rate\nwas ~2049 counts/sec (15-350 keV), at ~119 sec after the trigger. \n\nThe XRT began observing the field at 12:25:20.7 UT, 148.4 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 325.89615, 4.23548 which\nis equivalent to:\n   RA(J2000)  = 21h 43m 35.08s\n   Dec(J2000) = +04d 14' 07.7\"\nwith an uncertainty of 3.5 arcseconds (radius, 90% containment). This\nlocation is 68 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 consistent with the Galactic value of 6.84\nx 10^20 cm^-2 (Willingale et al. 2013). \n\nThe initial flux in the 2.5 s image was 7.01e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 158 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 100% of\nthe XRT error circle. The typical 3-sigma upper limit has been about 19.6 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 expected extinction corresponding to E(B-V) of\n0.077. \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",
  "submitter": "Jamie Kennea at Penn State <jak51@psu.edu>",
  "eventId": "GRB 240419B"
}