{
  "bibcode": "2021GCN.30497....1D",
  "body": "P. D'Avanzo (INAF-OAB), M. G. Bernardini (INAF-OAB),\nJ. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII),\nA. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),\nA. Melandri (INAF-OAB), D. M. Palmer (LANL) and T. Sbarrato (INAF-OAB)\nreport on behalf of the Neil Gehrels Swift Observatory Team:\n\nAt 20:14:09 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 210724A (trigger=1061482).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 227.407d, -6.274d which is \n   RA(J2000) = 15h 09m 38s\n   Dec(J2000) = -06d 16' 27\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty). Due to a telemetry outage the BAT lightcurve is\nnot immediately available.  However, the trigger information indicates\na duration of at least 4 seconds. \n\nThe XRT began observing the field at 20:17:09.0 UT, 179.8 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 227.4118,\n-6.2911 which is equivalent to:\n   RA(J2000)  = 15h 09m 38.83s\n   Dec(J2000) = -06d 17' 27.8\"\nwith an uncertainty of 1.9 arcseconds (radius, 90% containment). This\nposition may be improved as more data are received; the latest position\nis 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 8.23\nx 10^20 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 124 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\n0.097. \n\nBurst Advocate for this burst is P. D'Avanzo (paolo.davanzo AT inaf.it). \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/)",
  "circularId": 30497,
  "createdOn": 1627159048000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 210724A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 210724A"
}