GCN Circular 27526

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 70 observations of the LVC error region for the
GW trigger S200225q convolved with the 2MPZ catalogue (Bilicki et al.
2014, ApJS, 210, 9), using the 'LALInference' (version 1) 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 172 ks to 224 ks after the LVC trigger, and the XRT
has covered 3.8 deg^2 on the sky (corrected for overlaps). This covers
51% of the probability in the 'LALInference' (version 1) skymap, and
51% after convolving with the 2MPZ galaxy catalogue, as described by
Evans et al. (2016, MNRAS,  462, 1591). These pointings and associated
metadata have been reported to the Treasure Map (Wyatt et al., arXiv
2001.00588; http://treasuremap.space/alerts?graceids=S200225q).

We have detected 1 X-ray source. 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
  * 0 sources of rank 3
  * 1 source of rank 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   |
|   S200225q_X1  | 06h 42m 40.91s | +88d 04' 42.7" |	9.0" |

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/S200225q

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