A Compact Object (or Compact Star) is a collective term for White Dwarves, Neutron Stars, Black Holes (BH) 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 (GW) and a Luminosity (L) potentially 1015 that of the Sun.
Gravitational Wave (GW)
Nanohertz Gravitational Waves