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GCN Circular 25208

Subject
LIGO/Virgo S190728q: Update on Sky-Localization and Source-Classification
Date
2019-07-28T21:54:44Z (5 years ago)
From
Sarah Antier at APC <antier@apc.in2p3.fr>
The LIGO Scientific Collaboration and Virgo Collaboration report:

We have conducted further analysis of the LIGO and Virgo data around
the time of the compact binary coalescence (CBC) candidate S190728q
(GCN 25187). Parameter estimation has been performed using
LALInference [1] and a new sky map, LALInference.offline.fits.gz,
distributed via GCN Notice, is available for retrieval from the
GraceDB event page:

https://gracedb.ligo.org/superevents/S190728q/

LALInference.offline.fits.gz is the preferred sky map at this time.
The 90% credible region is 104 deg2. Marginalized over the whole sky,
the a posteriori luminosity distance estimate is 874 +/- 171 Mpc
(a posteriori mean +/- standard deviation).

Based on posterior support from parameter estimation [1,2], under the
assumption that the candidate S190728q is astrophysical in origin,
there is strong evidence against the hypothesis that the lighter
compact object has a mass < 3 solar masses (HasNS < 1%) and a
negligible probability of having disrupted material outside the final
compact object (HasRemnant < 1%). The parameter estimation based
classification of the GW signal, in order of descending probability,
is BBH (95%), MassGap (5%), NSBH (<1%), or BNS (<1%).

The above mentioned probabilities are based on full exploration of the
binary parameter space, and hence are the preferred classification
results that supersede the ones stated in GCN 25187.

The probability of non-astrophysical origin and the false alarm rate
are not being updated at this time; both measures of significance
should be expected to change with offline analyses and continued
observations.

For further information about analysis methodology and the contents
of this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.

[1] Veitch, et al. PRD 91, 042003 (2015)
[2] Abbott, et al. PRL 116, 241102 (2016)
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