GCN Circular 27951

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
locations are fictitious. ***

We identified the compact binary merger candidate
MS200615h during real-time processing of data from LIGO
Hanford Observatory (H1) and LIGO Livingston Observatory
(L1) at 2020-06-15 00:35:41.894 UTC (GPS time:
1276216559.894). The candidate was found by the GstLAL
[1] analysis Pipeline in the early warning configuration,
and an Early Warning GCN Notice was issued. The GCN
Notice included the standard data products associated
with CBC alerts, namely localization [2] and source
classification [3].

However, this Early Warning alert (MS200615h) is no
longer of interest because it was not detected by the
regular, full-bandwidth search.

[1] Messick et al. PRD 95, 042001 (2017)
[2] Singer & Price PRD 93, 024013 (2016)
[3] Chatterjee et al. The Astrophysical Journal 896, 1 (2020)