From LIGO@astrodon.social on Mastodon: While we're testing our detectors ahead of # O4 starting next week, we have identified our first interesting candidate # S230518h If real, the source is most likely a neutron star–black hole binary. Checks of the data quality are underway Circular: https:// gcn.nasa.gov/circulars/33813 # O4IsComing # GravitationalWaves 1/3