General-relativistic simulations of binary black hole-neutron stars: Precursor electromagnetic signals

We perform the first general relativistic force-free simulations of neutron star magnetospheres in orbit about spinning and nonspinning black holes. We find promising precursor electromagnetic emission: typical Poynting luminosities at, e.g., an orbital separation of r=6.6RNS are ${L}EM{~}6×{}{10}⁴²({B}NS,p/{10}¹³ G{)}²({M}NS/1.4{M}_{{}}{)}² erg/s$. The Poynting flux peaks within a broad beam of ${~}40^∘{}$ in the azimuthal direction and within ${~}60^∘{}$ from the orbital plane, establishing a possible lighthouse effect. Our calculations, though preliminary, preview more detailed simulations of these systems that we plan to perform in the future.