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GCN Circular 27965

LIGO/Virgo MS200615ce: Identification of a test binary black hole candidate
2020-06-16T13:07:05Z (4 years ago)
Surabhi Sachdev at LVC <>
The LIGO Scientific Collaboration and the Virgo Collaboration report:

*** This is a test of the Early Warning alert system resulting from archival
O3 data. Times and sky localizations are fictitious. ***

We identified the compact binary merger candidate MS200615ce during
real-time processing of data from LIGO Hanford Observatory (H1) and
Virgo Observatory (V1) at 2020-06-15 14:33:36.473 UTC (GPS time:
1276266834.473). The candidate was found by the GstLAL [1], PyCBC Live
[2], and MBTAOnline [3] analysis pipelines.

MS200615ce is an event of interest because its false alarm rate, as
estimated by the online analysis, is 9e-19 Hz, or about one in 1e11
years. The event's properties can be found at this URL:

The classification of the GW signal, in order of descending
probability, is MassGap (>99%), Terrestrial (<1%), BNS (<1%), BBH
(<1%), or NSBH (<1%).

Assuming the candidate is astrophysical in origin, the probability
that the lighter compact object has a mass < 3 solar masses (HasNS) is
19%. Using the masses and spins inferred from the signal, the
probability of matter outside the final compact object (HasRemnant) is

Two sky maps are available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz,0, an initial localization generated by BAYESTAR [4],
distributed via GCN notice about 52 seconds after the candidate event time.
 * bayestar.fits.gz,1, an initial localization generated by BAYESTAR [4],
distributed via GCN notice about 5 minutes after the candidate event time.

The preferred sky map at this time is bayestar.fits.gz,1. For the
bayestar.fits.gz,1 sky map, the 90% credible region is 354 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 330 +/- 79 Mpc (a posteriori mean +/- standard deviation).

For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide

 [1] Messick et al. PRD 95, 042001 (2017)
 [2] Nitz et al. PRD 98, 024050 (2018)
 [3] Adams et al. CQG 33, 175012 (2016)
 [4] Singer & Price PRD 93, 024013 (2016)
 [5] Singer & Price PRD 93, 024013 (2016)
 [6] Chatterjee et al. The Astrophysical Journal 896, 1 (2020)
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