{
  "bibcode": "2017GCN.21233....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), S.W.K. Emery (UCL-MSSL), P. Giommi (ASI), C. Gronwall\n(PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien\n(GSFC/UMBC), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), J.A.\nNousek (PSU), S.R. Oates (U. Warwick), P.T. O'Brien (U. Leicester),\nJ.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page\n(U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin\n(NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G.\nTagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on behalf of\nthe Swift team:\n\nSwift performed a four-pointing follow up of the possible LAT source in\nthe error region of GW trigger G288732 (Omodei et al., LVC Circ.\n21227). The observations currently span from 63 ks to 91 ks after the\nLVC Trigger, and we obtained 1.4-3.9 ks per field.\n\nWe have detected 7 X-ray sources. Sources 4&5 are known X-ray emitters\n(1RXS J083249.9+432322 and 1RXS J083409.3+431912 respectively). The\nremaining sources are uncatalogued and have fluxes consistent with\ncatalogue upper limits, and show no evidence for fading. We therefore\ncannot reliably associate any of these with either the possible LAT\ndetection or the GW event. Unfortunately, this region of the sky is now\nin Swift's Sun observing constraint until September, so no further\nfollow up will be conducted before that time.\n\nThe automated analysis assigns each source is a rank of 1-4 which\ndescribes how likely it is to be related to the GW trigger, with 1\nbeing the most likely and 4 being the least likely. The ranks are\ndescribed 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  * 4 sources of rank 3\n  * 2 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 1:\n  =============\n    RA: \t 128.2633 ( = 08h 33m 3.19s) J2000\n    Dec:\t +43.2130 ( = +43d 12' 46.8\") J2000\n    Error:\t +8.6 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 1.4e-02 +/- 1.1e-02 ct/sec (0.3-10 keV)\n    Peak Flux:\t 6.1e-13 +/- 4.6e-13 erg cm^-2 s^-1 (0.3-10 keV)\n    RASS UL:\t 1.4e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV)\n\n       so the source is not above the RASS 3-sigma upper limit.\n    The source may be fading, at the 0.6-sigma level.\n    There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source\n    and consistent (within 3-sigma) with the distance to the GW object.\n\n    A SIMBAD object `LEDA 2215540' is 6.4\" away.\n    There is 1 2MASS object within the source's 3-sigma error radius.\n  \n  Source 2:\n  =============\n    RA: \t 128.0321 ( = 08h 32m 7.70s) J2000\n    Dec:\t +43.4975 ( = +43d 29' 51.0\") J2000\n    Error:\t +5.7 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 3.9e-03 +/- 2.4e-03 ct/sec (0.3-10 keV)\n    Peak Flux:\t 1.7e-13 +/- 1.0e-13 erg cm^-2 s^-1 (0.3-10 keV)\n    RASS UL:\t 1.6e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV)\n\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 \n\n      object.\n  \n  Source 3:\n  =============\n    RA: \t 127.8821 ( = 08h 31m 31.70s) J2000\n    Dec:\t +43.4300 ( = +43d 25' 48.0\") J2000\n    Error:\t +6.3 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 1.3e-02 +/- 9.7e-03 ct/sec (0.3-10 keV)\n    Peak Flux:\t 5.4e-13 +/- 4.2e-13 erg cm^-2 s^-1 (0.3-10 keV)\n    RASS UL:\t 4.2e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV)\n\n       so the source is not above the RASS 3-sigma upper limit.\n    The source may be fading, at the 0.4-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 \n\n      object.\n  \n  Source 6:\n  =============\n    RA: \t 128.4283 ( = 08h 33m 42.79s) J2000\n    Dec:\t +43.2892 ( = +43d 17' 21.1\") J2000\n    Error:\t +5.0 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 5.1e-03 +/- 2.0e-03 ct/sec (0.3-10 keV)\n    Peak Flux:\t 2.2e-13 +/- 8.6e-14 erg cm^-2 s^-1 (0.3-10 keV)\n    RASS UL:\t 2.1e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV)\n\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 \n\n      object.\n    There is 1 2MASS object within the source's 3-sigma error radius.\n\n Source 7:\n  =============\n    RA: \t 127.8022 ( = 08h 31m 12.53s) J2000\n    Dec:\t +43.4288 ( = +43d 25' 43.7\") J2000\n    Error:\t +7.6 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 1.2e-02 +/- 7.4e-03 ct/sec (0.3-10 keV)\n    Peak Flux:\t 5.1e-13 +/- 3.2e-13 erg cm^-2 s^-1 (0.3-10 keV)\n    RASS UL:\t 3.2e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV)\n\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\n      object.\n    There is 1 2MASS object within the source's 3-sigma error radius.\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 4:\n  =============\n    RA: \t 128.2174 ( = 08h 32m 52.18s) J2000\n    Dec:\t +43.3858 ( = +43d 23' 08.9\") J2000\n    Error:\t +6.0 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 8.7e-03 +/- 5.4e-03 ct/sec (0.3-10 keV)\n    Peak Flux:\t 3.7e-13 +/- 2.3e-13 erg cm^-2 s^-1 (0.3-10 keV)\n    Cat Source:  1RXS J083249.9+432322 in the ROSAT/RASSFSC catalogue\n    Separation:  28.2\" from the XRT source\n    Cat Rate:\t 1.7e-02 +/- 8.5e-03 ct/sec \n    Cat Flux:\t 4.9e-13 +/- 2.4e-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    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\n      object.\n  \n  Source 5:\n  =============\n    RA: \t 128.5303 ( = 08h 34m 7.27s) J2000\n    Dec:\t +43.3192 ( = +43d 19' 09.1\") J2000\n    Error:\t +7.2 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 9.4e-03 +/- 5.8e-03 ct/sec (0.3-10 keV)\n    Peak Flux:\t 4.0e-13 +/- 2.5e-13 erg cm^-2 s^-1 (0.3-10 keV)\n    Cat Source:  1RXS J083409.3+431912 in the ROSAT/RASSFSC catalogue\n    Separation:  22.5\" from the XRT source\n    Cat Rate:\t 2.3e-02 +/- 1.1e-02 ct/sec \n    Cat Flux:\t 6.5e-13 +/- 3.1e-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 0.3-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 \n\n      object.\n\nThis circular is an official product of the Swift team.",
  "circularId": 21233,
  "createdOn": 1497017432000,
  "email": "pae9@leicester.ac.uk",
  "subject": "LIGO/Virgo G288732: Swift-XRT follow up of the putative LAT counterpart",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "LIGO/Virgo G288732"
}