EMRIs around $j=1$ black holes with synchronised hair

Understand

We study extreme mass ratio inspirals (EMRIs) due to an infalling Light Compact Object (LCO) onto a generic class of stationary and axi-symmetric massive compact objects (MCO - with or without a horizon).

• Using the quadrupole hybrid formalism we obtain a master formula for the evolution of the radius of the LCO and find qualitatively different behaviours depending on the geodesic structure of the MCO.
• We then specialize the MCO to a black hole with synchronised scalar hair (BHsSH).
• To allow a comparison with a highly spinning Kerr BH, we consider BHsSH with dimensionless spin, $j = 1$.