{
  "bibcode": "2017GCN.20798....1E",
  "body": "P.A. Evans (U. Leicester), J.A. Kennea (PSU), S.D. Barthelmy\n(NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld (UCL-MSSL),\nD.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G.\nCusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB),\nV.D'Elia(ASDC), P. Giommi (ASI), C. Gronwall (PSU), H.A. Krimm\n(CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), D.\nMalesani (DARK/NBI), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB),\nB. Mingo (U. Leicester),  J.A. Nousek (PSU), S.R. Oates (U. Warwick),\nP.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U.\nLeicester), K.L. Page (U.Leicester), D.M. Palmer (LANL), M. Perri\n(ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H.\nSiegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP)\nreport on behalf of the Swift team:\n\nSwift has performed a series of 1330 observations of galaxies (from the\n2MPZ catalogue) within the LVC error region for the GW trigger G275697,\nusing the 'bayestar' GW localisation map. As this is a 3D skymap,\ngalaxy distances were taken into account in selecting which ones to\nobserve. The observations currently span from 15 ks to 184 ks after the\nLVC trigger, and cover 160 sq degrees on the sky (corrected for\noverlaps). This covers 0.15 of the probability in the LVC skymap, and\n0.29 of the probability in the LVC map after convolving with the 2MPZ\ngalaxy catalogue, as described by Evans et al., (2016, MNRAS,  462,\n1591).\n\nSince the last Swift GCN, we have detected 6 X-ray sources, these are\neither new detections, or have been given a higher 'rank' than in the\nlast circular. Each source is assigned a rank of 1-4 which describes\nhow likely it is to be related to the GW trigger, with 1 being the most\nlikely and 4 being the least likely. The ranks are described at\nhttp://www.swift.ac.uk/ranks.php.\n\nWe have found:\n\n  * 0 sources of rank 1\n  * 0 sources of rank 2\n  * 1 source of rank 3\n  * 5 sources of rank 4\n\nFor all flux conversions and comparisons with catalogues and upper\nlimits from other missions, we assumed a power-law spectrum with\nNH=3e20 cm^2, and photon index (Gamma)=1.7\n\n\nRANK 3 sources\n==============\n\nThese are uncatalogued X-ray sources, however they are not brighter\nthan previous upper limits, so do not stand out as likely counterparts\nto the GW trigger.\n  \n  Source 8:\n  =============\n    RA: \t 17.4334 ( = 01h 09m 44.02s) J2000\n    Dec:\t +73.1996 ( = +73d 11' 58.6\") J2000\n    Error:\t +5.6 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 0.0e+00 +/- 0.0e+00 ct/sec (0.3-10 keV)\n    Peak Flux:\t 0.0e+00 +/- 0.0e+00 erg cm^-2 s^-1 (0.3-10 keV)\n    RASS UL:\t 0.0e+00 ct/sec, 3-sigma, converted to XRT (0.3-10 keV)\n       so the source is not above the RASS 3-sigma upper limit.\n    There is no evidence for fading.\n    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy\n      which is consistent (within 3-sigma) with the distance to the GW\nobject.\n\n\nRANK 4 sources\n==============\n\nThese are catalogued X-ray sources, showing no signs of outburst\ncompared to previous observations, so they are not likely to be related\nto the GW trigger.\n  \n  Source 2:\n  =============\n    RA: \t 153.9839 ( = 10h 15m 56.14s) J2000\n    Dec:\t -20.0412 ( = -20d 02' 28.3\") J2000\n    Error:\t +5.6 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 1.7e-01 +/- 6.0e-02 ct/sec (0.3-10 keV)\n    Peak Flux:\t 7.1e-12 +/- 2.6e-12 erg cm^-2 s^-1 (0.3-10 keV)\n    Cat Source:  1RXS J101556.7-200219 in the ROSAT/RASSBSC catalogue\n    Separation:  12.3\" from the XRT source\n    Cat Rate:\t 1.6e-01 +/- 2.3e-02 ct/sec \n    Cat Flux:\t 4.4e-12 +/- 6.3e-13 erg cm^-2 s^-1 (0.3-10 keV)\n       so the source  is 1.0-sigma above the catalogued flux.\n    There is no evidence for fading.\n    There are 2 GWGC or 2MPZ galaxies within 200 kpc of the source.\n      and consistent (within 3-sigma) with the distance to the GW\nobject.\n    A SIMBAD object `2MASX J10155660-2002268' is 6.9\" away.\n    There is 1 2MASS object within the source's 3-sigma error radius.\n  \n  Source 3:\n  =============\n    RA: \t 174.7569 ( = 11h 39m 1.66s) J2000\n    Dec:\t -37.7381 ( = -37d 44' 17.2\") J2000\n    Error:\t +4.2 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 9.8e-01 +/- 1.9e-01 ct/sec (0.3-10 keV)\n    Peak Flux:\t 4.2e-11 +/- 8.3e-12 erg cm^-2 s^-1 (0.3-10 keV)\n    Cat Source:  1SXPS J113901.5-374416 in the 1SXPS catalogue\n    Separation:  1.0\" from the XRT source\n    Cat Rate:\t 1.9e+00 +/- 1.5e-02 ct/sec \n    Cat Flux:\t 8.3e-11 +/- 6.4e-13 erg cm^-2 s^-1 (0.3-10 keV)\n       so the source is not above the catalogued flux.\n    The source may be fading, at the 1.1-sigma level.\n    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy\n      which is consistent (within 3-sigma) with the distance to the GW\nobject.\n    A SIMBAD object `NGC  3783' is 1.6\" away.\n    There is 1 2MASS object within the source's 3-sigma error radius.\n  \n  Source 4:\n  =============\n    RA: \t 174.0675 ( = 11h 36m 16.20s) J2000\n    Dec:\t -38.0356 ( = -38d 02' 08.2\") J2000\n    Error:\t +6.8 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 9.1e-02 +/- 3.5e-02 ct/sec (0.3-10 keV)\n    Peak Flux:\t 3.9e-12 +/- 1.5e-12 erg cm^-2 s^-1 (0.3-10 keV)\n    Cat Source:  1RXS J113616.1-380210 in the ROSAT/RASSBSC catalogue\n    Separation:  2.6\" from the XRT source\n    Cat Rate:\t 2.1e-01 +/- 2.7e-02 ct/sec \n    Cat Flux:\t 5.9e-12 +/- 7.5e-13 erg cm^-2 s^-1 (0.3-10 keV)\n       so the source is not above the catalogued flux.\n    There is no evidence for fading.\n    There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source.\n\n      and consistent (within 3-sigma) with the distance to the GW\nobject.\n    A SIMBAD object `V* V858 Cen' is 3.2\" away.\n    There are 2 2MASS objects within the source's 3-sigma error radius.\n  \n  Source 5:\n  =============\n    RA: \t 218.9470 ( = 14h 35m 47.28s) J2000\n    Dec:\t -52.6808 ( = -52d 40' 50.9\") J2000\n    Error:\t +5.9 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 1.9e-01 +/- 6.7e-02 ct/sec (0.3-10 keV)\n    Peak Flux:\t 8.0e-12 +/- 2.9e-12 erg cm^-2 s^-1 (0.3-10 keV)\n    Cat Source:  XMMSL1 J143548.8-524058 in the XMM-NEWTON/XMMSLEWCLN\ncatalogue\n    Separation:  6.9\" from the XRT source\n    Cat Rate:\t 1.7e+00 +/- 5.0e-01 ct/sec \n    Cat Flux:\t 1.7e-11 +/- 5.0e-12 erg cm^-2 s^-1 (0.3-10 keV)\n       so the source is not above the catalogued flux.\n    There is no evidence for fading.\n    There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source.\n\n      and consistent (within 3-sigma) with the distance to the GW\nobject.\n    A SIMBAD object `CD-52  6194' is 8.1\" away.\n    There is 1 2MASS object within the source's 3-sigma error radius.\n  \n  Source 6:\n  =============\n    RA: \t 325.6803 ( = 21h 42m 43.27s) J2000\n    Dec:\t +43.5868 ( = +43d 35' 12.5\") J2000\n    Error:\t +4.2 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 2.7e+00 +/- 4.2e-01 ct/sec (0.3-10 keV)\n    Peak Flux:\t 1.2e-10 +/- 1.8e-11 erg cm^-2 s^-1 (0.3-10 keV)\n    Cat Source:  1SXPS J214242.7+433509 in the 1SXPS catalogue\n    Separation:  5.9\" from the XRT source\n    Cat Rate:\t 1.8e+00 +/- 1.8e-02 ct/sec \n    Cat Flux:\t 7.7e-11 +/- 7.7e-13 erg cm^-2 s^-1 (0.3-10 keV)\n       so the source  is 2.2-sigma above the catalogued flux.\n    There is no evidence for fading.\n    There are 10 GWGC or 2MPZ galaxies within 200 kpc of the source.\n      and consistent (within 3-sigma) with the distance to the GW\nobject.\n    A SIMBAD object `V* SS Cyg' is 5.8\" away.\n    There is 1 2MASS object within the source's 3-sigma error radius.\n\nThis circular is an official product of the Swift team.",
  "circularId": 20798,
  "createdOn": 1488490267000,
  "email": "pae9@leicester.ac.uk",
  "subject": "LIGO/Virgo G275697: Further Swift-XRT sources",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "LIGO/Virgo G275697"
}