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GCN Circular 21503

Subject
LIGO/Virgo G297595: Swift-XRT sources
Date
2017-08-17T09:51:32Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), J.A. Kennea (PSU), S.D. Barthelmy
(NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld (UCL-MSSL),
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), H.A. Krimm (CRESST/GSFC/USRA), 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. Warwick), P.T. O'Brien (U. Leicester),
J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page
(U.Leicester), 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 performed a series of 535 observations, covering 535 separate
locations within the LVC error region for the GW trigger G297595 (LVC
Circ. 21474) convolved with the 2MPZ catalogue (Bilicki et al. 2014,
ApJS, 210, 9), using 530 fields from the 'bayestar' GW localisation map
and 5 fields from the 'LALInference' GW localisation map. As these are
3D skymaps, galaxy distances were taken into account in selecting which
ones to observe. The observations currently span from 31 ks to 222 ks
after the LVC trigger, and cover 54.6 sq degrees on the sky (corrected
for overlaps). This covers 13% of the probability in the 'LALInference'
skymap, and 17% after convolving with the 2MPZ galaxy catalogue, as
described by Evans et al., (2016, MNRAS,  462, 1591). Using the earlier
 'bayestar' skymap our observations covered 70% of the probability (70%
when convolved).

We have detected 7 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
  * 7 sources of rank 4

For all flux conversions and comparisons with catalogues and upper
limits from other missions, we assumed a power-law spectrum with
NH=3e20 cm^2, and photon index (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: 	 41.4741 ( = 02h 45m 53.78s) J2000
    Dec:	 -44.9939 ( = -44d 59' 38.0") J2000
    Error:	 +5.4 (arcsec, radius, 90% confidence).
    Peak Rate:	 8.1e-02 +/- 4.9e-02 ct/sec (0.3-10 keV)
    Peak Flux:	 3.5e-12 +/- 2.1e-12 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  1SXPS J024554.1-445938 in the 1SXPS catalogue
    Separation:  3.9" from the XRT source
    Cat Rate:	 7.9e-02 +/- 4.7e-03 ct/sec 
    Cat Flux:	 3.4e-12 +/- 2.0e-13 erg cm^-2 s^-1 (0.3-10 keV)
       so the source is not above the catalogued flux.
    There is no evidence for fading.
    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy
      which is consistent (within 3-sigma) with the distance to the GW
object.
    A SIMBAD object `QSO B0244-452' is 3.5" away.
    There is 1 2MASS object within the source's 3-sigma error radius.
  
  Source 2:
  =============
    RA: 	 38.6302 ( = 02h 34m 31.25s) J2000
    Dec:	 -46.5331 ( = -46d 31' 59.2") J2000
    Error:	 +6.3 (arcsec, radius, 90% confidence).
    Peak Rate:	 1.1e-01 +/- 5.3e-02 ct/sec (0.3-10 keV)
    Peak Flux:	 4.9e-12 +/- 2.3e-12 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  XMMSL2 J023431.2-463207 in the XMM-NEWTON/XMMSLEWCLN
catalogue
    Separation:  8.0" from the XRT source
    Cat Rate:	 9.0e-01 +/- 4.3e-01 ct/sec 
    Cat Flux:	 9.0e-12 +/- 4.3e-12 erg cm^-2 s^-1 (0.3-10 keV)
       so the source is not above the catalogued flux.
    The source may be fading, at the 0.2-sigma level.
    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy
      which is consistent (within 3-sigma) with the distance to the GW
object.
    A SIMBAD object `6dFGS gJ023431.3-463206' is 7.3" away.
    There is 1 2MASS object within the source's 3-sigma error radius.
  
  Source 3:
  =============
    RA: 	 34.6059 ( = 02h 18m 25.42s) J2000
    Dec:	 -50.2247 ( = -50d 13' 28.9") J2000
    Error:	 +5.7 (arcsec, radius, 90% confidence).
    Peak Rate:	 1.7e-02 +/- 6.4e-03 ct/sec (0.3-10 keV)
    Peak Flux:	 7.5e-13 +/- 2.7e-13 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  1SXPS J021825.9-501330 in the 1SXPS catalogue
    Separation:  5.4" from the XRT source
    Cat Rate:	 2.0e-02 +/- 4.1e-04 ct/sec 
    Cat Flux:	 8.8e-13 +/- 1.8e-14 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 are 3 GWGC or 2MPZ galaxies within 200 kpc of the source.
      and consistent (within 3-sigma) with the distance to the GW
object.
    A SIMBAD object `1RXS J021824.9-501335' is 7.7" away.
  
  Source 4:
  =============
    RA: 	 37.5016 ( = 02h 30m 0.38s) J2000
    Dec:	 -54.0222 ( = -54d 01' 19.9") J2000
    Error:	 +7.8 (arcsec, radius, 90% confidence).
    Peak Rate:	 4.6e-02 +/- 1.6e-02 ct/sec (0.3-10 keV)
    Peak Flux:	 2.0e-12 +/- 6.7e-13 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  3XMM J023001.4-540115 in the XMM-NEWTON/XMMSSC
catalogue
    Separation:  10.5" from the XRT source
    Cat Rate:	 7.9e-01 +/- 1.0e-02 ct/sec 
    Cat Flux:	 7.9e-12 +/- 1.0e-13 erg cm^-2 s^-1 (0.3-10 keV)
       so the source is not above the catalogued flux.
    There is no evidence for fading.
    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy
      which is consistent (within 3-sigma) with the distance to the GW
object.
  
  Source 5:
  =============
    RA: 	 37.5869 ( = 02h 30m 20.86s) J2000
    Dec:	 -54.2524 ( = -54d 15' 08.6") J2000
    Error:	 +5.2 (arcsec, radius, 90% confidence).
    Peak Rate:	 3.4e-02 +/- 1.2e-02 ct/sec (0.3-10 keV)
    Peak Flux:	 1.5e-12 +/- 5.0e-13 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  3XMM J023021.0-541506 in the XMM-NEWTON/XMMSSC
catalogue
    Separation:  2.3" from the XRT source
    Cat Rate:	 1.8e-01 +/- 4.7e-03 ct/sec 
    Cat Flux:	 1.8e-12 +/- 4.7e-14 erg cm^-2 s^-1 (0.3-10 keV)
       so the source is not above the catalogued flux.
    There is no evidence for fading.
    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy
      which is consistent (within 3-sigma) with the distance to the GW
object.
    There is 1 2MASS object within the source's 3-sigma error radius.
  
  Source 6:
  =============
    RA: 	 48.7127 ( = 03h 14m 51.05s) J2000
    Dec:	 -42.0480 ( = -42d 02' 52.8") J2000
    Error:	 +4.4 (arcsec, radius, 90% confidence).
    Peak Rate:	 3.6e-02 +/- 1.1e-02 ct/sec (0.3-10 keV)
    Peak Flux:	 1.6e-12 +/- 4.8e-13 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  XMMSL2 J031450.4-420243 in the XMM-NEWTON/XMMSLEWCLN
catalogue
    Separation:  11.5" from the XRT source
    Cat Rate:	 1.6e+00 +/- 7.1e-01 ct/sec 
    Cat Flux:	 1.6e-11 +/- 7.1e-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.
    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy
      which is consistent (within 3-sigma) with the distance to the GW
object.
  
  Source 7:
  =============
    RA: 	 48.4264 ( = 03h 13m 42.34s) J2000
    Dec:	 -41.9943 ( = -41d 59' 39.5") J2000
    Error:	 +4.9 (arcsec, radius, 90% confidence).
    Peak Rate:	 3.5e-02 +/- 1.1e-02 ct/sec (0.3-10 keV)
    Peak Flux:	 1.5e-12 +/- 4.6e-13 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  1RXS J031342.2-415934 in the ROSAT/RASSBSC catalogue
    Separation:  5.7" from the XRT source
    Cat Rate:	 7.9e-02 +/- 1.6e-02 ct/sec 
    Cat Flux:	 2.2e-12 +/- 4.5e-13 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 or 2MPZ galaxy within 200 kpc of the source.

      and consistent (within 3-sigma) with the distance to the GW
object.
    A SIMBAD object `2MASS J03134233-4159362' is 3.3" away.
    There is 1 2MASS object within the source's 3-sigma error radius.

This circular is an official product of the Swift team.
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