{
  "bibcode": "2019GCN.23989....1B",
  "body": "S. D. Barthelmy (GSFC), J.D. Gropp (PSU), A. Y. Lien (GSFC/UMBC),\nD. M. Palmer (LANL) and B. Sbarufatti (PSU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 20:30:47 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated LS I +61 303 (trigger=894557).  Swift slewed immediately to \nthe source. \nThe BAT on-board calculated location is \nRA, Dec 40.153, +61.246 which is \n   RA(J2000) = 02h 40m 37s\n   Dec(J2000) = +61d 14' 45\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed multiple short\nspikes with a total duration of about 20 sec.  The peak count rate\nwas ~2400 counts/sec (15-350 keV), at ~3 sec after the trigger. \n\nThe XRT began observing the field at 20:32:12.5 UT, 85.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find an X-ray source\nwith an enhanced position: RA, Dec 40.1330, 61.2290 which is equivalent\nto:\n   RA(J2000)  = 02h 40m 31.91s\n   Dec(J2000) = +61d 13' 44.2\"\nwith an uncertainty of 2.0 arcseconds (radius, 90% containment). This\nlocation is 70 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. This\nposition is 2.0 arcseconds from LS I +61 303. This source is in the \nSwift XRT 1SXPS catalogue with a mean 0.3-10 keV count-rate of \n0.19600 +/- 0.00093 ct/sec; see \nhttp://www.swift.ac.uk/1SXPS/1SXPSJ024031.5%2B611344 \nfor details of these previous observations. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of 9.01\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nUVOT data cannot properly be analyzed at this time. A full analysis\nwill be possible once the full dataset comes to the ground. \n\nThe light curve from the BAT transient monitor is available at\nhttps://swift.gsfc.nasa.gov/results/transients/weak/LSIp61303/",
  "circularId": 23989,
  "createdOn": 1553375783000,
  "email": "bxs60@psu.edu",
  "subject": "Swift detection of LS I +61 303",
  "submitter": "Boris Sbarufatti at PSU  <bxs60@psu.edu>"
}