{
  "bibcode": "2018GCN.22752....1C",
  "body": "S. B. Cenko (GSFC), J.D. Gropp (PSU), A. Y. Lien (GSFC/UMBC),\nA. Melandri (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL)\nand M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 08:14:50 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 180602A (trigger=835200).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 142.339, +32.093 which is \n   RA(J2000) = 09h 29m 21s\n   Dec(J2000) = +32d 05' 34\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The burst appears to have been in progress\nas Swift was slewing to the pre-planned pointing target before the\nnominal trigger time.  The BAT light curve showed a single peak\nstructure with a duration of about 50 seconds, however the start\nof the peak may be due to the GRB entering the FOV during the slew. \nThe peak count rate was ~1300 counts/sec (15-350 keV), at ~20 sec \nbefore the trigger. \n\nThe XRT began observing the field at 08:16:55.2 UT, 124.3 seconds after\nthe BAT trigger. The position determined from promptly downlinked data\ndiffers significantly from the on-board position, suggesting that the\nXRT may have centroided on a cosmic ray; the initial XRT position\nnotice should be treated with caution. Using promptly downlinked data\nwe find an uncatalogued X-ray source with an enhanced position: RA, Dec\n142.3319, 32.0661 which is equivalent to:\n   RA(J2000)  = 09h 29m 19.65s\n   Dec(J2000) = +32d 03' 58.1\"\nwith an uncertainty of 2.2 arcseconds (radius, 90% containment). This\nlocation is 99 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 http://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 (1.56 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.1\n(+2.76/-2.42) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 133 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\n0.02. \n\nBurst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). \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/too.html.)",
  "circularId": 22752,
  "createdOn": 1527928507000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 180602A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 180602A"
}