GCN Circular 18732

P.A. Evans (U. Leicester), J.A. Kennea (PSU), Scott Barthelmy
(NASA/GSFC), Dave Burrows (PSU), Sergio Campana (INAF-OAB), Brad Cenko
(NASA/GSFC), Neil Gehrels (NASA/GSFC), Paolo Giommi (ASI), Frank
Marshall (NASA/GSFC), John Nousek (PSU), Paul O'Brien (U. Leicester),
Julian Osborne (U. Leicester), Kim Page (U. Leicester), David Palmer
(LANL), Matteo Perri (ASDC), Judy Racusin (NASA/GSFC), Mike Siegel
(PSU), Gianpiero Tagliaferri (INAF-OAB) report on behalf of the Swift
team:

Swift has performed a series of 24 observations of galaxies (from the
GWGC catalogue) within the aLIGO error region for the aLIGO trigger
G211117, using the 'bayestar' GW localisation map. The observations
currently span from 140 ks to 164 ks after the aLIGO trigger, and cover
2.8 sq degrees on the sky (corrected for overlaps). Further
observations are ongoing.

We have detected 2 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 http://www.swift.ac.uk/ranks.php.

We have found:

  * 0 sources of rank 1
  * 0 sources of rank 2
  * 0 sources of rank 3
  * 2 sources of rank 4

We assumed a power-law spectrum with NH=3e20 cm^2, and Gamma=1.7

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 1:
  =============
    RA: 	 207.3302 ( = 13h 49m 19.25s)  J2000
    Dec:	 -30.3100 ( = -30d 18' 36.0")  J2000
    Error:	 +4.1 (radius, 90% confidence).
    Peak Rate:	 1.0e+00 +/- 2.4e-01 ct/sec (0.3-10 keV)
    Peak Flux:	 4.4e-11 +/- 1.0e-11 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  1SXPS J134919.2-301834 in the 1SXPS catalogue
    Separation:  1.5" from the XRT source
    Cat Rate:	 2.6e+00 +/- 2.6e-02 ct/sec (0.3-10 keV)
    Cat Flux:	 1.1e-10 +/- 1.1e-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 galaxy within 200 kpc of the source.
    A SIMBAD object `RXC J1349.3-3018' is 2.1" away
    There are 3 2MASS objects within the source's 3-sigma error radius
  
  Source 2:
  =============
    RA: 	 202.5292 ( = 13h 30m 7.01s)  J2000
    Dec:	 -21.6998 ( = -21d 41' 59.3")  J2000
    Error:	 +5.2 (radius, 90% confidence).
    Peak Rate:	 6.2e-02 +/- 1.5e-02 ct/sec (0.3-10 keV)
    Peak Flux:	 2.7e-12 +/- 6.3e-13 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  1RXS J133006.8-214156 in the ROSAT/RASSFSC catalogue
    Separation:  3.9" from the XRT source
    Cat Rate:	 8.3e-02 +/- 2.4e-02 ct/sec (0.3-10 keV)
    Cat Flux:	 2.3e-12 +/- 6.9e-13 erg cm^-2 s^-1 (0.3-10 keV)
       So the source  is 0.3-sigma above the catalogued flux
    There is no evidence for fading
    NOTE: this source is not within 200 kpc of a GWGC galaxy.
    A SIMBAD object `[RKV2003] QSO J1330-2142 abs 0.3014' is 2.9" away
    There is 1 2MASS object within the source's 3-sigma error radius

This circular is an official product of the Swift team.