{
  "bibcode": "2019GCN.24541....1E",
  "body": "P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (PSU), S.D.\nBarthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld\n(UCL-MSSL), D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko\n(NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P.\nD'Avanzo (INAF-OAB), V.D'Elia(ASDC), S.W.K. Emery (UCL-MSSL), P. Giommi\n(ASI), C. Gronwall (PSU), D. Hartmann (U. Clemson), H.A. Krimm\n(CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), F.E.\nMarshall (NASA/GSFC), A. Melandri (INAF-OAB), J.A. Nousek (PSU), S.R.\nOates (U. Warwick), P.T. O'Brien (U. Leicester), J.P. Osborne (U.\nLeicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), D.M.\nPalmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti\n(INAF-OAB/PSU), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja\n(NASA/GSFC/UMCP) report on behalf of the Swift team:\n\nSwift has performed a series of 977 observations, covering 977 separate\nlocations within the LVC error region for the GW trigger S190510g\nconvolved with the 2MPZ catalogue (Bilicki et al. 2014, ApJS, 210, 9),\nusing 226 fields from the 'bayestar' GW localisation map and 751 fields\nfrom the 'LALInference' GW localisation map. As these are 3D skymaps,\ngalaxy distances were taken into account in selecting which ones to\nobserve. The observations currently span from 7.2 ks to 270 ks after\nthe LVC trigger, and cover 76.9 sq degrees on the sky (corrected for\noverlaps). This covers 58% of the probability in the 'LALInference'\nskymap, and 67% after convolving with the 2MPZ galaxy catalogue, as\ndescribed by Evans et al., (2016, MNRAS,  462, 1591). Using the earlier\n'bayestar' skymap our observations cover 10% of the probability (14%\nwhen convolved).\n\nWe have detected 33 X-ray sources. Each source is assigned a rank of\n1-4 which describes how likely it is to be related to the GW trigger,\nwith 1 being the most likely and 4 being the least likely. The ranks\nare described at http://www.swift.ac.uk/ranks.php.\n\nWe have found:\n\n   * 0 sources of rank 1\n   * 0 sources of rank 2\n   * 5 sources of rank 3\n   * 28 sources of rank 4\n\nDetails of these sources can be viewed online via \nhttp://www.swift.ac.uk/LVC/\n\nFor all GW triggers from O3 onwards, XRT results will appear on this \npage, once human verification has taken place to remove spurious sources.\n\nAdditionally, our search serendipitously covered the locations of some \nof the other reported candidates. In particular the location of \nDG19fqqk/desgw-190510c (GCNs 24467, 24480) was covered 4 times. No XRT \nsource was found with a 3-sigma upper limit of 6.1 x 10^-2 ct/sec, \ncorresponding to a 0.3-10 keV flux of 2.6 x 10^-12 erg cm^-2 s^-1. The \nlocation of DG19llhk (GCNs 24467) was covered 3 times with no detection \nfound, down to a  3-sigma upper limit of 6.4 x 10^-2 ct/sec, \ncorresponding to 2.8e-12 erg cm^-2 s^-1. Both flux conversions assume a \npower-law spectrum with photon index=1.7 and absorption column NH=3 x \n10^20 cm^-2.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 24541,
  "createdOn": 1557845783000,
  "email": "pae9@leicester.ac.uk",
  "subject": "LIGO/Virgo S190510g: Swift-XRT observations and results",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "LIGO/Virgo S190510g"
}