{
  "createdOn": 1692203081569,
  "circularId": 34450,
  "subject": "GRB 230816A: Swift detection of a burst",
  "body": "\nM. H. Siegel (PSU), S. Dichiara (PSU),\nR. A. J. Eyles-Ferris (U Leicester), J.D. Gropp (PSU),\nJ. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU),\nK. L. Page (U Leicester), D. M. Palmer (LANL),\nT. M. Parsotan (GSFC/UMBC/CRESSTII), B. Sbarufatti (INAF-OAB) and\nM. A. Williams (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 16:08:48 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 230816A (trigger=1185673).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 328.375, +37.828 which is \n   RA(J2000) = 21h 53m 30s\n   Dec(J2000) = +37d 49' 43\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single-peaked\nstructure with a duration of about 25 sec.  The peak count rate\nwas ~1900 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 16:10:18.4 UT, 90.2 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 328.44552,\n37.85549 which is equivalent to:\n   RA(J2000)  = 21h 53m 46.92s\n   Dec(J2000) = +37d 51' 19.8\"\nwith an uncertainty of 1.9 arcseconds (radius, 90% containment). This\nlocation is 223 arcseconds from the BAT onboard position. This position\nmay be improved as more data are received; the latest position is\navailable 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 (2.90 x\n10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.7\n(+3.48/-2.91) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 93 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 0.311. \n\nBurst Advocate for this burst is M. H. Siegel (siegel AT swift.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": "David Palmer at LANL <palmer@lanl.gov>",
  "bibcode": "2023GCN.34450....1S",
  "submittedHow": "email",
  "eventId": "GRB 230816A"
}