[vsnet-grb-info 23450] LIGO/Virgo S190426c: Update on Probability of Terrestrial Origin

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25549
SUBJECT: LIGO/Virgo S190426c: Update on Probability of Terrestrial Origin
DATE:    19/08/29 14:46:43 GMT
FROM:    Deep Chatterjee at University of Wisconsin, Milwaukee  <deep at uwm.edu>

The LIGO Scientific Collaboration and Virgo Collaboration report:

A revised computation of the classification of the candidate based on
detection-pipeline-specific foreground and background models is
available. The probability of the source being of terrestrial origin
is now estimated to be 58% in contrast to the original estimation of
14% in  GCN Circular 24237. This revision was necessitated by a
bug-fix in the source-classification code. This same bug-fix was used
to update the event candidate S190510g, as reported in GCN Circular
24462. We apologize for the delay in updating the information for this
event.

The estimated false alarm rate is unchanged at 1.9e-08 Hz, or about
one per 1.6 years. Note that future offline analyses may infer a
different terrestrial probability and/or false alarm rate.

The new p_astro.json file in GraceDB at
https://gracedb.ligo.org/superevents/S190426c/ reports that the
revised classification of the candidate is Terrestrial (58%),
BNS (24%), MassGap (12%), NSBH (6%) and BBH (<1%). Note that the
parameter estimation based classification reported in GCN Circular
24411 is unchanged: Assuming that the candidate S190426c is
astrophysical in origin, the relative probabilities amongst the signal
categories NSBH : MassGap : BNS : BBH are approximately 12 : 5 : 3 : 0
based on posterior support.