TITLE: GCN CIRCULAR NUMBER: 20812 SUBJECT: LIGO/Virgo G275697: Further Swift-XRT sources DATE: 17/03/04 09:38:16 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), J.A. Kennea (PSU), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld (UCL-MSSL), D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V.D'Elia(ASDC), P. Giommi (ASI), C. Gronwall (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), D. Malesani (DARK/NBI), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester), J.A. Nousek (PSU), S.R. Oates (U. Warwick), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team: Swift has performed a series of 1385 observations of galaxies (from the 2MPZ catalogue) within the LVC error region for the GW trigger G275697, using the 'bayestar' GW localisation map. As this is a 3D skymap, galaxy distances were taken into account in selecting which ones to observe. The observations currently span from 15 ks to 350 ks after the LVC trigger, and cover 167 sq degrees on the sky (corrected for overlaps). This covers 0.16 of the probability in the LVC skymap, and 0.30 of the probability in the LVC map after convolving with the 2MPZ galaxy catalogue, as described by Evans et al., (2016, MNRAS, 462, 1591). Since the last Swift GCN, we have detected 15 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. Many more sources were reported via GCN/LVC_COUNTERPART notices, which had the "WARN_FLAG" field set to 1, indicating that the automatic detection system considered the sources may be spurious. Manual inspection has confirmed these sources are not real, but were caused by stray light - singly-reflected X-rays from a bright, off-axis source. See http://www.swift.ac.uk/1SXPS/construct.php#fig5 more details. The new, manually verified sources comprise: * 0 sources of rank 1 * 0 sources of rank 2 * 6 sources of rank 3 * 9 sources of rank 4 For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3e20 cm^2, and photon index (Gamma)=1.7 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 18: ============= RA: 230.8241 ( = 15h 23m 17.78s) J2000 Dec: -50.4510 ( = -50d 27' 03.6") J2000 Error: +6.2 (arcsec, radius, 90% confidence). Peak Rate: 3.7e-02 +/- 1.2e-02 ct/sec (0.3-10 keV) Peak Flux: 1.6e-12 +/- 5.0e-13 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 2.6e-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 or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. There are 3 2MASS objects within the source's 3-sigma error radius. Source 19: ============= RA: 221.4244 ( = 14h 45m 41.86s) J2000 Dec: -49.3746 ( = -49d 22' 28.6") J2000 Error: +6.7 (arcsec, radius, 90% confidence). Peak Rate: 1.9e-02 +/- 8.1e-03 ct/sec (0.3-10 keV) Peak Flux: 8.2e-13 +/- 3.5e-13 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 2.2e-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. There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source. and consistent (within 3-sigma) with the distance to the GW object. Source 23: ============= RA: 323.3099 ( = 21h 33m 14.38s) J2000 Dec: +39.6853 ( = +39d 41' 07.1") J2000 Error: +5.5 (arcsec, radius, 90% confidence). Peak Rate: 6.4e-02 +/- 3.9e-02 ct/sec (0.3-10 keV) Peak Flux: 2.8e-12 +/- 1.7e-12 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 1.6e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. The source may be fading, at the 1.5-sigma level. NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. There is 1 2MASS object within the source's 3-sigma error radius. Source 24: ============= RA: 142.4443 ( = 09h 29m 46.63s) J2000 Dec: +2.0633 ( = +02d 03' 47.9") J2000 Error: +6.0 (arcsec, radius, 90% confidence). Peak Rate: 5.4e-02 +/- 4.1e-02 ct/sec (0.3-10 keV) Peak Flux: 2.3e-12 +/- 1.8e-12 erg cm^-2 s^-1 (0.3-10 keV) 1XMM UL: 5.7e-12 ct/sec, (0.3-10 keV) so the source is 1.9-sigma above the XMM 3-sigma upper limit. RASS UL: 1.7e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. The source may be fading, at the 0.9-sigma level. There are 5 GWGC or 2MPZ galaxies within 200 kpc of the source. and consistent (within 3-sigma) with the distance to the GW object. A SIMBAD object `NGC 2898' is 6.3" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 25: ============= RA: 154.6980 ( = 10h 18m 47.52s) J2000 Dec: -18.5442 ( = -18d 32' 39.1") J2000 Error: +5.1 (arcsec, radius, 90% confidence). Peak Rate: 4.6e-02 +/- 3.4e-02 ct/sec (0.3-10 keV) Peak Flux: 2.0e-12 +/- 1.5e-12 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 2.1e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV) so the source is not above the RASS 3-sigma upper limit. The source may be fading, at the 1.2-sigma level. NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. Source 30: ============= RA: 150.6904 ( = 10h 02m 45.70s) J2000 Dec: -16.1968 ( = -16d 11' 48.5") J2000 Error: +5.6 (arcsec, radius, 90% confidence). Peak Rate: 2.0e-02 +/- 8.5e-03 ct/sec (0.3-10 keV) Peak Flux: 8.6e-13 +/- 3.7e-13 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 1.7e-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 or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. 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 15: ============= RA: 175.6993 ( = 11h 42m 47.83s) J2000 Dec: -35.8159 ( = -35d 48' 57.2") J2000 Error: +4.7 (arcsec, radius, 90% confidence). Peak Rate: 1.2e-01 +/- 5.9e-02 ct/sec (0.3-10 keV) Peak Flux: 5.0e-12 +/- 2.6e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: XMMSL1 J114247.5-354904 in the XMM-NEWTON/XMMSLEWCLN catalogue Separation: 8.8" from the XRT source Cat Rate: 0.0e+00 +/- 0.0e+00 ct/sec Cat Flux: 0.0e+00 +/- 0.0e+00 erg cm^-2 s^-1 (0.3-10 keV) so the source is not above the catalogued flux. The source may be fading, at the 1.3-sigma level. NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. A SIMBAD object `V* V752 Cen' is 3" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 16: ============= RA: 333.9766 ( = 22h 15m 54.38s) J2000 Dec: +52.3104 ( = +52d 18' 37.4") J2000 Error: +6.1 (arcsec, radius, 90% confidence). Peak Rate: 1.5e-02 +/- 6.4e-03 ct/sec (0.3-10 keV) Peak Flux: 6.5e-13 +/- 2.8e-13 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J221553.6+521752 in the ROSAT/RASSFSC catalogue Separation: 46.2" from the XRT source Cat Rate: 2.4e-02 +/- 6.8e-03 ct/sec Cat Flux: 6.8e-13 +/- 1.9e-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 or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. There are 2 2MASS objects within the source's 3-sigma error radius. Source 17: ============= RA: 335.0252 ( = 22h 20m 6.05s) J2000 Dec: +53.0105 ( = +53d 00' 37.8") J2000 Error: +8.6 (arcsec, radius, 90% confidence). Peak Rate: 1.5e-02 +/- 6.9e-03 ct/sec (0.3-10 keV) Peak Flux: 6.3e-13 +/- 3.0e-13 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J222010.7+530025 in the ROSAT/RASSFSC catalogue Separation: 43.8" from the XRT source Cat Rate: 1.9e-02 +/- 6.4e-03 ct/sec Cat Flux: 5.2e-13 +/- 1.8e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 0.3-sigma above the catalogued flux. There is no evidence for fading. There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source. and consistent (within 3-sigma) with the distance to the GW object. There are 6 2MASS objects within the source's 3-sigma error radius. Source 20: ============= RA: 146.7595 ( = 09h 47m 2.28s) J2000 Dec: -5.9474 ( = -05d 56' 50.6") J2000 Error: +5.7 (arcsec, radius, 90% confidence). Peak Rate: 1.7e-02 +/- 8.9e-03 ct/sec (0.3-10 keV) Peak Flux: 7.3e-13 +/- 3.8e-13 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: XMMSL1 J094702.8-055704 in the XMM-NEWTON/XMMSLEWCLN catalogue Separation: 15.8" from the XRT source Cat Rate: 5.9e-01 +/- 2.1e-01 ct/sec Cat Flux: 5.9e-12 +/- 2.1e-12 erg cm^-2 s^-1 (0.3-10 keV) so the source is not above the catalogued flux. There is no evidence for fading. There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source. and consistent (within 3-sigma) with the distance to the GW object. A SIMBAD object `LEDA 1038543' is 8.3" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 21: ============= RA: 152.9971 ( = 10h 11m 59.30s) J2000 Dec: -16.6088 ( = -16d 36' 31.7") J2000 Error: +5.0 (arcsec, radius, 90% confidence). Peak Rate: 3.9e-02 +/- 1.1e-02 ct/sec (0.3-10 keV) Peak Flux: 1.7e-12 +/- 4.6e-13 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J101158.2-163617 in the ROSAT/RASSFSC catalogue Separation: 21.1" from the XRT source Cat Rate: 3.7e-02 +/- 1.1e-02 ct/sec Cat Flux: 1.0e-12 +/- 3.1e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.1-sigma above the catalogued flux. There is no evidence for fading. There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source. and consistent (within 3-sigma) with the distance to the GW object. A SIMBAD object `2MASX J10115905-1636329' is 3.7" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 22: ============= RA: 227.5239 ( = 15h 10m 5.74s) J2000 Dec: -50.8594 ( = -50d 51' 33.8") J2000 Error: +5.9 (arcsec, radius, 90% confidence). Peak Rate: 9.4e-02 +/- 4.8e-02 ct/sec (0.3-10 keV) Peak Flux: 4.0e-12 +/- 2.1e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J151006.2-505125 in the ROSAT/RASSFSC catalogue Separation: 9.7" from the XRT source Cat Rate: 2.4e-02 +/- 1.1e-02 ct/sec Cat Flux: 6.7e-13 +/- 3.1e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.6-sigma above the catalogued flux. The source may be fading, at the 2.0-sigma level. There are 2 GWGC or 2MPZ galaxies within 200 kpc of the source. and consistent (within 3-sigma) with the distance to the GW object. There are 4 2MASS objects within the source's 3-sigma error radius. Source 27: ============= RA: 314.7183 ( = 20h 58m 52.39s) J2000 Dec: +31.5034 ( = +31d 30' 12.2") J2000 Error: +5.8 (arcsec, radius, 90% confidence). Peak Rate: 1.7e-02 +/- 6.3e-03 ct/sec (0.3-10 keV) Peak Flux: 7.5e-13 +/- 2.7e-13 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 2E 2056.7+3118 in the EINSTEIN/EINSTEIN2E catalogue Separation: 9.9" from the XRT source Cat Rate: 1.6e-02 +/- 3.2e-03 ct/sec Cat Flux: 7.7e-13 +/- 1.5e-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 or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. There are 2 2MASS objects within the source's 3-sigma error radius. Source 29: ============= RA: 318.4372 ( = 21h 13m 44.93s) J2000 Dec: +35.5312 ( = +35d 31' 52.3") J2000 Error: +6.1 (arcsec, radius, 90% confidence). Peak Rate: 2.7e-02 +/- 9.6e-03 ct/sec (0.3-10 keV) Peak Flux: 1.1e-12 +/- 4.1e-13 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J211341.2+353144 in the ROSAT/RASSFSC catalogue Separation: 46.3" from the XRT source Cat Rate: 2.2e-02 +/- 9.5e-03 ct/sec Cat Flux: 6.2e-13 +/- 2.7e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.0-sigma above the catalogued flux. There is no evidence for fading. NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. There is 1 2MASS object within the source's 3-sigma error radius. Source 32: ============= RA: 155.8947 ( = 10h 23m 34.73s) J2000 Dec: -19.5432 ( = -19d 32' 35.5") J2000 Error: +5.2 (arcsec, radius, 90% confidence). Peak Rate: 5.3e-02 +/- 4.0e-02 ct/sec (0.3-10 keV) Peak Flux: 2.3e-12 +/- 1.7e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J102335.1-193240 in the ROSAT/RASSFSC catalogue Separation: 7.2" from the XRT source Cat Rate: 2.1e-02 +/- 9.2e-03 ct/sec Cat Flux: 5.9e-13 +/- 2.6e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.0-sigma above the catalogued flux. The source may be fading, at the 1.3-sigma level. There are 2 GWGC or 2MPZ galaxies within 200 kpc of the source. and consistent (within 3-sigma) with the distance to the GW object. A SIMBAD object `TYC 6068-295-1' is 4.4" away. There is 1 2MASS object within the source's 3-sigma error radius. This circular is an official product of the Swift team.