{
  "bibcode": "2015GCN.17261....1V",
  "body": "A. Vargas (PSU), W. H. Baumgartner (GSFC/UMBC),\nJ. R. Cummings (NASA/UMBC), H. A. Krimm (CRESST/GSFC/USRA),\nB. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf\nof the Swift Team:\n\nAt 06:28:53 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 150101A (trigger=623158).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 312.631, +36.728 which is \n   RA(J2000) = 20h 50m 31s\n   Dec(J2000) = +36d 43' 39\"\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 0.1 sec.  The peak count rate\nwas ~3700 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 06:29:54.4 UT, 60.9 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source with an enhanced position: RA, Dec 312.6038, 36.7334 which\nis equivalent to:\n   RA(J2000)  = 20h 50m 24.91s\n   Dec(J2000) = +36d 44' 00.3\"\nwith an uncertainty of 3.9 arcseconds (radius, 90% containment). This\nlocation is 80 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 4.62\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White\nfilter  starting 65 seconds after the BAT trigger. No credible\nafterglow candidate has  been found in the initial data products. The\n2.7'x2.7' sub-image covers 100% of  the XRT error circle. The 8'x8'\nregion for the list of sources generated on-board covers 100% of the\nXRT error circle. Because of the density of catalogued stars,  further\nanalysis is required to report an upper limit for any afterglow in the\n region. No correction has been made for the large, but uncertain\nextinction  expected. \n\nBurst Advocate for this burst is A. Vargas (vargas.09242011.angie 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": 17261,
  "createdOn": 1420095213000,
  "email": "hans.krimm@nasa.gov",
  "subject": "GRB 150101A: Swift detection of a short burst",
  "submitter": "Hans Krimm at NASA-GSFC  <hans.krimm@nasa.gov>",
  "eventId": "GRB 150101A"
}