TITLE: GCN CIRCULAR NUMBER: 20798 SUBJECT: LIGO/Virgo G275697: Further Swift-XRT sources DATE: 17/03/02 21:31:07 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 1330 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 184 ks after the LVC trigger, and cover 160 sq degrees on the sky (corrected for overlaps). This covers 0.15 of the probability in the LVC skymap, and 0.29 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 6 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 * 1 source of rank 3 * 5 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 8: ============= RA: 17.4334 ( = 01h 09m 44.02s) J2000 Dec: +73.1996 ( = +73d 11' 58.6") J2000 Error: +5.6 (arcsec, radius, 90% confidence). Peak Rate: 0.0e+00 +/- 0.0e+00 ct/sec (0.3-10 keV) Peak Flux: 0.0e+00 +/- 0.0e+00 erg cm^-2 s^-1 (0.3-10 keV) RASS UL: 0.0e+00 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 2: ============= RA: 153.9839 ( = 10h 15m 56.14s) J2000 Dec: -20.0412 ( = -20d 02' 28.3") J2000 Error: +5.6 (arcsec, radius, 90% confidence). Peak Rate: 1.7e-01 +/- 6.0e-02 ct/sec (0.3-10 keV) Peak Flux: 7.1e-12 +/- 2.6e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J101556.7-200219 in the ROSAT/RASSBSC catalogue Separation: 12.3" from the XRT source Cat Rate: 1.6e-01 +/- 2.3e-02 ct/sec Cat Flux: 4.4e-12 +/- 6.3e-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. 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 `2MASX J10155660-2002268' is 6.9" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 3: ============= RA: 174.7569 ( = 11h 39m 1.66s) J2000 Dec: -37.7381 ( = -37d 44' 17.2") J2000 Error: +4.2 (arcsec, radius, 90% confidence). Peak Rate: 9.8e-01 +/- 1.9e-01 ct/sec (0.3-10 keV) Peak Flux: 4.2e-11 +/- 8.3e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1SXPS J113901.5-374416 in the 1SXPS catalogue Separation: 1.0" from the XRT source Cat Rate: 1.9e+00 +/- 1.5e-02 ct/sec Cat Flux: 8.3e-11 +/- 6.4e-13 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 1.1-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 `NGC 3783' is 1.6" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 4: ============= RA: 174.0675 ( = 11h 36m 16.20s) J2000 Dec: -38.0356 ( = -38d 02' 08.2") J2000 Error: +6.8 (arcsec, radius, 90% confidence). Peak Rate: 9.1e-02 +/- 3.5e-02 ct/sec (0.3-10 keV) Peak Flux: 3.9e-12 +/- 1.5e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J113616.1-380210 in the ROSAT/RASSBSC catalogue Separation: 2.6" from the XRT source Cat Rate: 2.1e-01 +/- 2.7e-02 ct/sec Cat Flux: 5.9e-12 +/- 7.5e-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. 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 `V* V858 Cen' is 3.2" away. There are 2 2MASS objects within the source's 3-sigma error radius. Source 5: ============= RA: 218.9470 ( = 14h 35m 47.28s) J2000 Dec: -52.6808 ( = -52d 40' 50.9") J2000 Error: +5.9 (arcsec, radius, 90% confidence). Peak Rate: 1.9e-01 +/- 6.7e-02 ct/sec (0.3-10 keV) Peak Flux: 8.0e-12 +/- 2.9e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: XMMSL1 J143548.8-524058 in the XMM-NEWTON/XMMSLEWCLN catalogue Separation: 6.9" from the XRT source Cat Rate: 1.7e+00 +/- 5.0e-01 ct/sec Cat Flux: 1.7e-11 +/- 5.0e-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 `CD-52 6194' is 8.1" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 6: ============= RA: 325.6803 ( = 21h 42m 43.27s) J2000 Dec: +43.5868 ( = +43d 35' 12.5") J2000 Error: +4.2 (arcsec, radius, 90% confidence). Peak Rate: 2.7e+00 +/- 4.2e-01 ct/sec (0.3-10 keV) Peak Flux: 1.2e-10 +/- 1.8e-11 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1SXPS J214242.7+433509 in the 1SXPS catalogue Separation: 5.9" from the XRT source Cat Rate: 1.8e+00 +/- 1.8e-02 ct/sec Cat Flux: 7.7e-11 +/- 7.7e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 2.2-sigma above the catalogued flux. There is no evidence for fading. There are 10 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 `V* SS Cyg' is 5.8" away. There is 1 2MASS object within the source's 3-sigma error radius. This circular is an official product of the Swift team.