TITLE: GCN CIRCULAR NUMBER: 18870 SUBJECT: LIGO/Virgo G211117: Further Swift-XRT sources DATE: 16/01/15 12:20:10 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), J.A. Kennea (PSU), S.D. Barthelmy (NASA/GSFC), D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), N. Gehrels (NASA/GSFC), P. Giommi (ASI), F.E. Marshall (NASA/GSFC), J.A. Nousek (PSU), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB) report on behalf of the Swift team: Swift has performed a series of 264 observations of galaxies (from the GWGC catalogue) within the aLIGO error region for the aLIGO trigger G211117, using the 'bayestar' GW localisation map. The observations currently span from 140 ks to 1677 ks after the aLIGO trigger, and cover 32.3 sq degrees on the sky (corrected for overlaps). Since the last Swift GCN, we have detected 8 X-ray sources, these are either new detections, or have been given a higher 'rank' than in the last circular. Each source is assigned a rank of 1-4 which describes how likely it is to be related to the GW trigger, with 1 being the most likely and 4 being the least likely. The ranks are described at http://www.swift.ac.uk/ranks.php. We have found: * 0 sources of rank 1 * 0 sources of rank 2 * 6 sources of rank 3 * 2 sources of rank 4 We assumed a power-law spectrum with NH=3e20 cm^2, and photon index (Gamma)=1.7 Several other sources were circulated as GCN/LVC Counterpart notices (including one with a rank of 2) with a flag identifying them as potentially spurious. Manual inspection of the images confirms that these were not point sources, but artifacts caused by an area of diffuse X-ray emission, centred on RA~02h 32m 37s Dec~+18d 44' 10", with a radius of ~0.6 arcmin. RANK 3 sources ============== These are uncatalogued X-ray sources, however they are not brighter than previous upper limits, so do not stand out as likely counterparts to the GW trigger. Source 56: ============= RA: 38.0971 ( = 02h 32m 23.30s) J2000 Dec: +18.5781 ( = +18d 34' 41.2") J2000 Error: +5.9 (arcsec, radius, 90% confidence). Peak Rate: 2.2e-03 +/- 6.4e-04 ct/sec (0.3-10 keV) Peak Flux: 9.5e-14 +/- 2.7e-14 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 1.2e-01 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. There is no evidence for fading. NOTE: this source is not within 200 kpc of a GWGC galaxy. Source 57: ============= RA: 38.0905 ( = 02h 32m 21.72s) J2000 Dec: +18.6325 ( = +18d 37' 57.0") J2000 Error: +6.8 (arcsec, radius, 90% confidence). Peak Rate: 3.1e-03 +/- 8.1e-04 ct/sec (0.3-10 keV) Peak Flux: 1.3e-13 +/- 3.5e-14 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 1.4e-01 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. There is no evidence for fading. NOTE: this source is not within 200 kpc of a GWGC galaxy. Source 59: ============= RA: 38.1497 ( = 02h 32m 35.93s) J2000 Dec: +18.7140 ( = +18d 42' 50.4") J2000 Error: +7.6 (arcsec, radius, 90% confidence). Peak Rate: 1.0e-03 +/- 4.4e-04 ct/sec (0.3-10 keV) Peak Flux: 4.4e-14 +/- 1.9e-14 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 8.1e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. There is no evidence for fading. NOTE: this source is not within 200 kpc of a GWGC galaxy. Source 61: ============= RA: 38.2965 ( = 02h 33m 11.16s) J2000 Dec: +18.5393 ( = +18d 32' 21.5") J2000 Error: +11.5 (arcsec, radius, 90% confidence). Peak Rate: 1.1e-03 +/- 4.6e-04 ct/sec (0.3-10 keV) Peak Flux: 4.8e-14 +/- 2.0e-14 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 6.1e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. There is no evidence for fading. NOTE: this source is not within 200 kpc of a GWGC galaxy. Source 65: ============= RA: 38.1408 ( = 02h 32m 33.79s) J2000 Dec: +18.6392 ( = +18d 38' 21.1") J2000 Error: +7.6 (arcsec, radius, 90% confidence). Peak Rate: 1.3e-03 +/- 5.1e-04 ct/sec (0.3-10 keV) Peak Flux: 5.7e-14 +/- 2.2e-14 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 9.0e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. There is no evidence for fading. NOTE: this source is not within 200 kpc of a GWGC galaxy. Source 67: ============= RA: 38.0820 ( = 02h 32m 19.68s) J2000 Dec: +18.7338 ( = +18d 44' 01.7") J2000 Error: +5.9 (arcsec, radius, 90% confidence). Peak Rate: 1.2e-03 +/- 5.1e-04 ct/sec (0.3-10 keV) Peak Flux: 5.2e-14 +/- 2.2e-14 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 1.3e-01 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. There is no evidence for fading. NOTE: this source is not within 200 kpc of a GWGC galaxy. RANK 4 sources ============== These are catalogued X-ray sources, showing no signs of outburst compared to previous observations, so they are not likely to be related to the GW trigger. Source 63: ============= RA: 136.1544 ( = 09h 04m 37.06s) J2000 Dec: +55.5974 ( = +55d 35' 50.6") J2000 Error: +6.9 (arcsec, radius, 90% confidence). Peak Rate: 1.5e-01 +/- 5.9e-02 ct/sec (0.3-10 keV) Peak Flux: 6.5e-12 +/- 2.5e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1SXPS J090436.8+553600 in the 1SXPS catalogue Separation: 10.3" from the XRT source Cat Rate: 1.7e-01 +/- 4.0e-03 ct/sec (0.3-10 keV) Cat Flux: 7.2e-12 +/- 1.7e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is not above the catalogued flux. There is no evidence for fading. NOTE: this source is not within 200 kpc of a GWGC galaxy. A SIMBAD object `2MASX J09043675+5535515' is 2.7" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 64: ============= RA: 153.7665 ( = 10h 15m 3.96s) J2000 Dec: +49.4331 ( = +49d 25' 59.2") J2000 Error: +5.0 (arcsec, radius, 90% confidence). Peak Rate: 2.0e+00 +/- 4.4e-01 ct/sec (0.3-10 keV) Peak Flux: 8.5e-11 +/- 1.9e-11 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1SXPS J101504.1+492559 in the 1SXPS catalogue Separation: 1.7" from the XRT source Cat Rate: 1.3e+00 +/- 7.7e-03 ct/sec (0.3-10 keV) Cat Flux: 5.6e-11 +/- 3.3e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.5-sigma above the catalogued flux. There is no evidence for fading. NOTE: this source is not within 200 kpc of a GWGC galaxy. A SIMBAD object `6C 101157+494057' is 2.3" away. There is 1 2MASS object within the source's 3-sigma error radius. This circular is an official product of the Swift team.