Gravitational wave fluxes on generic orbits in near-extreme Kerr spacetime: higher spin and large eccentricity

Abstract: To obtain the waveform template of gravitational waves (GWs), substantial computational resources and exceedingly high precision are often required. In the previous study [JCAP 11 (2023) 070], we efficiently and accurately calculate GW fluxes of a particle in circular orbits around a Schwarzschild black hole using the confluent Heun function. We extend the previous method to calculate the asymptotic GW fluxes from a particle in generic orbits around a near-extreme Kerr black hole. Especially when dealing with the computational difficulties in large eccentricity $e=0.9$, higher spin $a=0.999$, higher harmonic modes, and strong-field regions, our results are much better than the results of the numerical integration method based on the Mano-Suzuki-Takasugi method.