{
  "bibcode": "2017GCN.20964....1K",
  "body": "A. Keivani (PSU), D. B. Fox (PSU), P.A. Evans (U. Leicester), J.A.\nKennea (PSU), G. Tesic (PSU), D.F. Cowen (PSU), and J.P. Osborne (U.\nLeicester) report on behalf of the Swift-IceCube collaboration:\n\n\nSwift has observed the field of the IceCube EHE neutrino,\nIceCube-170321A (https://gcn.gsfc.nasa.gov/gcn3/20929.gcn3), utilizing\nthe on-board 7-point tiling pattern to cover a region centered on the\ninitial automated alert position RA,Dec (J2000) = (98.3268, -14.4861),\nwith a radius of approximately 0.55 degrees. This covers about 21% of\nthe 90% error region of the refined IceCube localization.\n\nSwift-XRT collected ~880 s per field of PC mode data per tile. The\nobservations were taken between 14:09:02 on 2017-03-21 and 18:03:00 on\n2017-03-21 (i.e. from 23.7 ks to 37.8 ks after the neutrino trigger),\nand covered 0.77 square degrees.\n\nAnalysis using standard Swift tools yields >3-sigma detection of a\nsingle X-ray source, 1SXPS J063214.5-143300, which is also seen in\nprevious observations of the field by Swift XRT, in a similar flux and\nspectral state. As such we conclude that there are no candidate X-ray\ncounterparts to the possibly-cosmic high-energy neutrino within the\ncovered region. Our 3-sigma upper limit on the count rate of any such\ncounterpart is 3.6e-3 XRT ct s-1, which corresponds to a 0.3-10 keV\nflux of 1.48e-13 erg cm-2 s-1 for a typical afterglow/AGN power-law\nspectrum with photon index gamma=1.7 and equivalent hydrogen column\ndensity N_H=3e+20 cm-2.\n\nDetails of the detected X-ray source are below.\n\nSource 1\n========\nRA:          06h 32m 14.5s = 98.06042d \t\nDec:         -14d 32' 59.9\" = -14.55000d\nError:       6.0 arcsec (90% confidence radius)\nCount rate:  (2.2 +/- 0.6) x 10^-2 ct s^-1\nFlux:        (9.0 +/- 2.5) x 10^-13 erg cm^-2 s^-1     Notes:\nThis source has been previously detected by Swift (1SXPS\nJ063214.5-143300) and the observed flux is consistent with the\ncatalogued value.",
  "circularId": 20964,
  "createdOn": 1490990000000,
  "email": "keivani@psu.edu",
  "subject": "IceCube-170321A: Swift-XRT observations",
  "submitter": "Azadeh Keivani at PSU  <keivani@psu.edu>",
  "eventId": "IceCube-170321A"
}