A Compact Object (or Compact Star) is a collective term for White Dwarves, Neutron Stars, Black Holes and other hypothesized exotic dense stars, which often are Stellar Remnants, what's left after a star's Fusion has run out. The term Degenerate Star is also used for compact objects that are not black holes. A Compact Object Merger is a merger of two such stars, the source of hypothesized detectable Gravitational Waves and a Luminosity potentially 1015 that of the Sun.
Gravitational Wave (GW)
Nanohertz Gravitational Waves