{
  "bibcode": "2015GCN.17269....1H",
  "body": "L. M. Z. Hagen (PSU), J. R. Cummings (NASA/UMBC),\nN. Gehrels (NASA/GSFC), M.E. Gropp (PSU), J. A. Kennea (PSU),\nH. A. Krimm (CRESST/GSFC/USRA) and M. H. Siegel (PSU) report on behalf\nof the Swift Team:\n\nAt 20:02:18 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 150103A (trigger=623368).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 131.639, -48.890 which is \n   RA(J2000) = 08h 46m 33s\n   Dec(J2000) = -48d 53' 24\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single peak about\n40 seconds long.  The peak count rate was ~875 counts/sec (15-350 keV), \nat ~5 sec after the trigger. \n\nThe XRT began observing the field at 20:04:29.5 UT, 130.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 131.66761, -48.88595 which is\nequivalent to:\n   RA(J2000)  = 08h 46m 40.23s\n   Dec(J2000) = -48d 53' 09.4\"\nwith an uncertainty of 3.8 arcseconds (radius, 90% containment). This\nlocation is 69 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.  We\ncannot determine whether the source is fading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of 8.96\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 135 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 large, but uncertain extinction expected. \n\nBurst Advocate for this burst is L. M. Z. Hagen (lea.zernow.hagen AT gmail.com). \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": 17269,
  "createdOn": 1420316257000,
  "email": "gehrels@milkyway.gsfc.nasa.gov",
  "subject": "GRB 150103A: Swift detection of a burst",
  "submitter": "Neil Gehrels at GSFC  <gehrels@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 150103A"
}