{
  "bibcode": "2021GCN.30485....1S",
  "body": "T. Sbarrato (INAF-OAB), M. G. Bernardini (INAF-OAB),\nP. D'Avanzo (INAF-OAB), J. A. Kennea (PSU),\nN. J. Klingler (GSFC/UMBC/CRESSTII), N. P. M. Kuin (UCL-MSSL),\nS. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC),\nF. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),\nD. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto)\nreport on behalf of the Neil Gehrels Swift Observatory Team:\n\nAt 14:46:10 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 210723A (trigger=1061284).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 121.726, -32.889 which is \n   RA(J2000) = 08h 06m 54s\n   Dec(J2000) = -32d 53' 20\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex\nstructure with a duration of about 50 sec.  The peak count rate\nwas ~2200 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 14:47:40.4 UT, 89.6 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source located at RA, Dec 121.72157,\n-32.88624 which is equivalent to:\n   RA(J2000)  = 08h 06m 53.18s\n   Dec(J2000) = -32d 53' 10.5\"\nwith an uncertainty of 7.0 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 7.70\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nThe initial flux in the 2.5 s image was 3.04e-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 99 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. Because of the density of catalogued stars, further\nanalysis is required to report an upper limit for any afterglow in the\nsub-image. The 8'x8' region for the list of sources generated on-board covers\n100% of the XRT error circle. Because of the density of catalogued stars,\nfurther analysis is required to report an upper limit for any afterglow in the\nregion. No correction has been made for the large, but uncertain, extinction\nexpected. \n\nAlthough the data from this burst are consistent with a classical long\nGRB, we note that this source is close to the Galactic plane \n(lat = -0.34 degrees) which raises the possibility that this is\na Galactic transient.  If further analysis determines that to be\nthe case, we would name the object Swift J0806.9-3253 . \n\nBurst Advocate for this burst is T. Sbarrato (tullia.sbarrato 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": 30485,
  "createdOn": 1627052687000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 210723A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 210723A"
}