TITLE: GCN CIRCULAR NUMBER: 26498 SUBJECT: LIGO/Virgo S191216ap, Swift XRT observations: 16 X-ray sources in the HAWC error region search DATE: 19/12/19 09:22:13 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), P. Brown (TAMU), 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), S.W.K. Emery (UCL-MSSL), P. Giommi (ASI), C. Gronwall (PSU), D. Hartmann (U. Clemson), H.A. Krimm (CRESST/GSFC/USRA), N.J. Klingler (PSU), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), J.A. Nousek (PSU), S.R. Oates (U. Birmingham), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), M.J.Page (UCL-MSSL), 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 carried out further observations of S191216ap. We performed a series of tiles to cover the HAWC error region (GCN Circ. 26472) for 500 s per tile, and then 3ks observations of each of the galaxies listed by Singer et al (GCN Circ. 26479). All of the Swift pointings and associated metadata have been reported to the Treasure Map (Wyatt et al., GCN Circ. 26244; http://treasuremap.space/alerts?graceids=S191216ap). In these observations, we detected 17 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 https://www.swift.ac.uk/ranks.php. We have found: * 0 sources of rank 1 * 0 sources of rank 2 * 13 sources of rank 3 * 4 sources of rank 4 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 ID | RA | Dec | Err90 | | S191216ap_X4 | 21h 33m 49.19s | +04d 57' 18.9" | 6.7" | | S191216ap_X5 | 21h 33m 18.81s | +05d 17' 04.9" | 6.9" | | S191216ap_X6 | 21h 34m 53.19s | +05d 19' 11.0" | 6.6" | | S191216ap_X7 | 21h 32m 44.20s | +04d 20' 06.0" | 5.8" | | S191216ap_X8 | 21h 32m 47.89s | +04d 27' 52.2" | 5.5" | | S191216ap_X9 | 21h 32m 26.75s | +04d 21' 31.6" | 5.3" | | S191216ap_X10 | 21h 32m 6.50s | +04d 18' 38.2" | 6.9" | | S191216ap_X12 | 21h 31m 46.59s | +05d 44' 44.4" | 7.0" | | S191216ap_X13 | 21h 31m 56.80s | +05d 11' 22.4" | 8.0" | | S191216ap_X17 | 21h 31m 43.77s | +05d 25' 15.7" | 6.0" | | S191216ap_X19 | 21h 31m 57.63s | +04d 43' 38.4" | 7.4" | | S191216ap_X20 | 21h 31m 31.98s | +04d 54' 03.0" | 5.0" | | S191216ap_X21 | 21h 31m 44.49s | +05d 23' 12.0" | 7.4" | 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 ID | RA | Dec | Err90 | | S191216ap_X11 | 21h 32m 41.01s | +04d 24' 18.6" | 6.2" | | S191216ap_X14 | 21h 30m 32.91s | +05d 02' 18.4" | 7.6" | | S191216ap_X15 | 21h 30m 26.31s | +05d 06' 07.0" | 7.2" | | S191216ap_X16 | 21h 31m 22.64s | +05d 02' 37.5" | 5.4" | For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2, and photon index (Gamma)=1.7 The results of the XRT automated analysis, including details of the sources listed above, are online at https://www.swift.ac.uk/LVC/S191216ap This circular is an official product of the Swift XRT team.