TITLE: GCN CIRCULAR NUMBER: 39009 SUBJECT: LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources DATE: 25/01/22 07:51:46 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
K.L. Page (U. Leicester), P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris (U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), J.J. Delaunay (PSU), M. De Pasquale (University of Messina), S. Dichiara (PSU), P. D’Avanzo (INAF-OAB), A. D’Aì (INAF-IASFPA) , V. D’Elia (ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin (UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P. Osborne (U. Leicester), P. O’Brien (U. Leicester), M.J. Page (UCL-MSSL), G. Raman (PSU) S. Ronchini (PSU), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team:
Swift has carried out 189 observations of the LVC error region for the GW trigger S250119cv convolved with the 2MPZ catalogue (Bilicki et al. 2014, ApJS, 210, 9), using the 'BAYESTAR' (version BAYESTAR.fits.gz) 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 2.6 ks to 101 ks after the LVC trigger, and the XRT has covered 13.1 deg^2 on the sky (corrected for overlaps). This covers 68% of the probability in the 'ligo-skymap-from-samples' (version ligo-skymap-from-samples.fits.gz) skymap, and 69% after convolving with the 2MPZ galaxy catalogue, as described by Evans et al. (2016, MNRAS, 462, 1591).
We have detected 5 X-ray sources. 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 * 1 source 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 | | S250119cv_X6 | 03h 47m 22.56s | -74d 14' 45.7" | 8.9" |
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 | | S250119cv_X1 | 00h 56m 18.41s | +27d 53' 48.0" | 7.4" | | S250119cv_X4 | 00h 55m 50.96s | +26d 24' 41.2" | 12.8" | | S250119cv_X5 | 00h 58m 11.65s | +27d 34' 36.6" | 6.7" | | S250119cv_X11 | 00h 58m 29.90s | +26d 39' 11.5" | 8.7" |
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, unless otherwise stated.
The results of the XRT automated analysis, including details of the sources listed above, are online at https://www.swift.ac.uk/LVC/S250119cv
This circular is an official product of the Swift XRT team.
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