TITLE: GCN CIRCULAR NUMBER: 27990 SUBJECT: LIGO/Virgo MS200618aq: Retraction of a test binary neutron star candidate DATE: 20/06/19 13:16:34 GMT FROM: Ryan Magee 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 MS200618aq during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2020-06-18 05:47:57.119 UTC (GPS time: 1276494495.119). The candidate was found by the GstLAL [1] analysis pipeline in the early warning configuration. An Early Warning GCN Notice was issued 39 seconds before the projected merger time. The GCN Notice included the standard data products associated with CBC alerts, namely localization [2] and source classification [3]. However, this Early Warning alert (MS200618aq) 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)