{
  "bibcode": "2019GCN.24405....1K",
  "body": "IceCube-190504A: Swift-XRT Follow-up Observations\n\nA. Keivani (Columbia U.), D. B. Fox (PSU), P. A. Evans (U. Leicester), J.\nA. Kennea (PSU), M. Santander (U. Alabama), & F. Krauss (GRAPPA/API,\nUniversity of Amsterdam) report:\n\n\nThe Neil Gehrels Swift Observatory observed the field of the IceCube HESE\nastrophysical neutrino candidate event IceCube-190504A (revision 1,\nhttps://gcn.gsfc.nasa.gov/gcn3/24392.gcn3) beginning May 4, 20:09:37 UT\n(1.74 hours after the neutrino arrival time).\n\nSwift utilized its onboard 19-point tiling pattern to cover a region\ncentered on R.A., Dec. (J2000) = 65.7866d, -37.4431d, with a radius of\napproximately 0.8 deg; estimated 90%-containment radius for this event is\n1.23 deg. Swift-XRT collected ~800 s per field of PC mode data per tile\nbetween 20:12:40 UT on 4 May and 09:08:01 UT on 5 May. Data have been\nreduced using the analysis approach and software routines of Evans et al.\n2014 (ApJS, 210, 8).\n\nSeveral X-ray sources are detected in these observations, most of which are\npreviously uncataloged and relatively low in flux, consistent with\nexpectations for serendipitous (unrelated) sources over a region of this\nextent. The highest-significance X-ray source is located at R.A. 66.17568d,\nDec. -37.93938d (J2000), 35 arcmin away from the neutrino direction, and\nmatches the known (SIMBAD) X-ray source QSO B0422-380 (1.4 arcsec away) as\nwell as 1SXPS J042442.5-375618 (6 arcsec away). We recover it at a mean\nobserved XRT count rate of 3.2 (+0.8, -0.7) e-2 ct s^-1, consistent with\n(1.5-sigma above) the cataloged flux from 1SXPS. Although the brightness of\nthis object does not look significantly elevated over the previous Swift\nobservations, it is catalogued as a blazar and would be interesting if\nthere is other electromagnetic emission from this source. Fermi-LAT has\nreported (GCN Circular #24401) significant emission at gamma ray over a\ntimescale of one week before the neutrino arrival time (at a flux level\nconsistent with the 10 years average) but no recent remarkable activity at\ngamma rays.\n\nExcluding identified sources, the 3-sigma upper limit on the count rate of\nany point-like counterpart over the rest of the tiled region is 0.01 ct\ns^-1, which corresponds to a 0.3-10 keV flux of 4.0e-13 erg cm^-2 s^-1 for\na typical AGN spectrum (nH=3e20 cm^-2, Gamma=1.7).\n\nCoordinates, count rates, and possible counterparts for the X-ray sources\nare provided below.\n\nSource, RA, Dec, Error_90 (arcsec), XRT count rate (ct s^-1), Possible\ncounterparts\n\n------------------------------------------------------------------------------------------------------------------\n\n#1: 66.17568d, -37.93938d, 7.9, 3.2 (+0.8, -0.7) e-2, QSO B0422-380 (1.4\narcsec away) & 1SXPS J042442.5-375618 (6 arcsec away)\n\n------------------------------------------------------------------------------------------------------------------\n\n#2: 66.39382d, -37.70566d, 6.6, 1.3 (+0.7, -0.5) e-2, 1RXS J042532.5-374212\n(25.4 arcsec away)\n\n------------------------------------------------------------------------------------------------------------------\n\n#3: 65.19589d, -37.26399d, 9.5, 1.0 (+0.6, -0.4) e-2, 1RXS J042449.3-365537\n(13.2 arcsec away)\n\n------------------------------------------------------------------------------------------------------------------\n\n#4: 66.20972d, -36.92833d, 6.3, 1.4 (+0.6, -0.5) e-2, --\n\n------------------------------------------------------------------------------------------------------------------\n\n#5: 65.70905d, -37.94807d, 7.5, 1.2 (+0.6, -0.5) e-2, --\n\n------------------------------------------------------------------------------------------------------------------\n\n#6: 66.39458d, -37.70534d, 7.9, 1.3 (+0.7, -0.5) e-2, 1RXS J042532.5-374212\n(27.1 arcsec away)\n\n------------------------------------------------------------------------------------------------------------------\n\n#7: 65.29548d, -38.09169d, 10.5, 1.3 (+0.6, -0.5) e-2, 1RXS\nJ042110.9-380533 (2.9 arcsec away)",
  "circularId": 24405,
  "createdOn": 1557140422000,
  "email": "azadeh.keivani@columbia.edu",
  "subject": "IceCube-190504A: Swift-XRT Follow-up Observations",
  "submitter": "Azadeh Keivani at Columbia U  <azadeh.keivani@columbia.edu>",
  "eventId": "IceCube-190504A"
}