{
  "subject": "GRB 121229A: Swift detection of a burst",
  "eventId": "GRB 121229A",
  "bibcode": "2012GCN.14115....1S",
  "createdOn": 1356758129000,
  "circularId": 14115,
  "submitter": "Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>",
  "email": "siegel@swift.psu.edu",
  "body": "E. Sonbas (NASA/GSFC/Adiyaman Univ.), V. D'Elia (ASDC),\nJ. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), T. Sakamoto (AGU)\nand M. H. Siegel (PSU) report on behalf of the Swift Team:\n\nAt 05:00:21 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 121229A (trigger=544347).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 190.100, -50.594 which is \n  RA(J2000) = 12h 40m 24s\n  Dec(J2000) = -50d 35' 37\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  Since this is an image trigger, the BAT light \ncurve does not show any particular structure.  The peak count rate \nwas ~1000 counts/sec (15-350 keV), at ~5 sec after the trigger. \n\nThe XRT began observing the field at 05:02:47.8 UT, 145.9 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 190.09755, -50.59366 which\nis equivalent to:\n  RA(J2000)  = 12h 40m 23.41s\n  Dec(J2000) = -50d 35' 37.2\"\nwith an uncertainty of 4.1 arcseconds (radius, 90% containment). This\nlocation is 5.7 arcseconds from the BAT onboard position, within the\nBAT error circle. This position may be improved as more data are\nreceived; the latest position is available at\nhttp://www.swift.ac.uk/sper.  We cannot determine whether the source is\nfading 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 1.35\nx 10^21 cm^-2 (Kalberla et al. 2005). \n\nThe initial flux in the 2.5 s image was 1.21e-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 155 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\n0.16. \n\nBurst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.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.)"
}