{
  "bibcode": "2017GCN.20390....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), N. Gehrels (NASA/GSFC), 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), D. Malesani (DARK/NBI), F.E. Marshall (NASA/GSFC), A.\nMelandri (INAF-OAB), B. Mingo (U. Leicester),  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 targetted observation of the interesting\ntransient ATLAS17aeu (Tonry et al., LVC Circ. 20382). The observations\nran from 00:00 UT to 01:37 UT on 2017 Jan 7, and contained 1.4 ks of\ncleaned PC mode data.\n\nA faint, uncatalouged X-ray source is found at RA, Dec = 138.3059,\n+61.0919 degrees, which corresponds to:\n\nRA (J2000):  09h 13m 13.42s\nDec (J2000): +61d 05' 30.8\") \n\nwith an uncertainty of 6.3 arcsec (radius, 90% confidence). This is\n4.1\" from the position of ATLAS17aeu, consitent with that object.\n\nThis source (\"source5\" of the XRT follow up of G268556) has a 0.3-10\nkeV count rate of 7.2 (+/-2.9) ��10^-3 ct s^-1, corresponding to a\n0.3-10 keV flux of 3.1 (+/-1.2) ��10^-13 erg cm^-2 s^-1, assuming a\npower-law spectrum with Gamma=1.7 and NH=3e20 cm^-2. This is below the\nupper limit derived from the RASS at the source location. This source\nhas not been previously observed by public XMM data, or Swift\nobservations.\n\nAt the present time we cannot ascertain whether the source is variable,\nbut follow up in encouraged.\n\n\nA second, catalogued (\"rank 4\") source is also detected in our\nobservations. Details of both sources are below.\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 5:\n  =============\n    RA: \t 138.3059 ( = 09h 13m 13.42s) J2000\n    Dec:\t +61.0919 ( = +61d 05' 30.8\") J2000\n    Error:\t +6.3 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 7.2e-03 +/- 2.9e-03 ct/sec (0.3-10 keV)\n    Peak Flux:\t 3.1e-13 +/- 1.2e-13 erg cm^-2 s^-1 (0.3-10 keV)\n    RASS UL:\t 1.8e-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\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 4:\n  =============\n    RA: \t 138.0838 ( = 09h 12m 20.11s) J2000\n    Dec:\t +60.9299 ( = +60d 55' 47.6\") J2000\n    Error:\t +5.1 (arcsec, radius, 90% confidence).\n    Peak Rate:\t 1.6e-02 +/- 4.4e-03 ct/sec (0.3-10 keV)\n    Peak Flux:\t 6.7e-13 +/- 1.9e-13 erg cm^-2 s^-1 (0.3-10 keV)\n    Cat Source:  1RXS J091222.2+605603 in the ROSAT/RASSFSC catalogue\n    Separation:  22.1\" from the XRT source\n    Cat Rate:\t 2.5e-02 +/- 9.4e-03 ct/sec \n    Cat Flux:\t 7.1e-13 +/- 2.6e-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\nobject.\n    A SIMBAD object `2MASS J09122029+6055503' is 3.1\" 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": 20390,
  "createdOn": 1483796016000,
  "email": "pae9@leicester.ac.uk",
  "subject": "LIGO/Virgo G268556: Swift-XRT detection of ATLAS17aeu",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "LIGO/Virgo G268556"
}