What happens when a neutron star is swallowed whole by a companion black hole? For a typical merger scenario, the lack of matter left outside the remnant black hole is thought to make such mergers quiet in electromagnetic bands. However, if the infalling neutron star harbors a strong magnetic field and is surrounded with tenuous, highly magnetized plasma (magnetosphere), a strong disturbance in the circumbinary magnetosphere can drive powerful electromagnetic bursts.
Our recent paper (led by Yoonsoo Kim and Elias Most at Caltech) exploring the magnetospheric dynamics of a black hole–neutron star binary, being on the AAS research highlight today, reveals that the merger can launch strongly magnetized (“monster”) shocks outward which may power radio bursts.
Furthermore, the remnant black hole exhibits a recently proposed “black hole pulsar” state, launching a decaying striped wind of plasma. Our study reveals a novel type of shock-powered and reconnection-driven transients associated with compact binary mergers.