GCN Circular 38324

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 observations of the BAT-GUANO error region for
the GW trigger S241125n (DeLaunay et al., GCN Circ. 38308
Not found
 
 
). The
observations currently span from 55 ks to 74 ks after the LVC trigger,
and the XRT has covered 0.2 deg^2 on the sky. This covers the entirety
of the GUANO error region, 2.80e-03% of the probability in the
'ligo-skymap-from-samples' (version ligo-skymap-from-samples.fits.gz)
skymap, and 2.49e-03% 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
  * 5 sources of rank 3
  * 0 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   |
|   S241125n_X1  | 03h 53m 28.81s | +69d 51' 22.6" |	5.8" |
|   S241125n_X2  | 03h 53m 19.82s | +69d 33' 09.2" |	5.8" |
|   S241125n_X3  | 03h 52m 24.85s | +69d 38' 25.9" |	7.9" |
|   S241125n_X4  | 03h 51m 13.98s | +69d 49' 22.4" |	6.3" |
|   S241125n_X5  | 03h 51m 08.80s | +69d 38' 37.3" |	6.7" |

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/S241125n

This circular is an official product of the Swift XRT team.