Publikace ÚTF

We present a new computation of the asymptotic gravitational wave energy fluxes emitted by a spinning
particle in circular equatorial orbits about a Kerr black hole. The particle dynamics is computed in the
pole-dipole approximation, solving the Mathisson-Papapetrou equations with the Tulczyjew spinsupplementary-
condition. The fluxes are computed, for the first time, by solving the 2 þ 1 Teukolsky
equation in the time-domain using hyperboloidal and horizon-penetrating coordinates. Denoting by M the
black hole mass and by μ the particle mass, we cover dimensionless background spins a=M ¼ ð0;0.9Þ
and dimensionless particle spins −0.9 ≤ S=μ2 ≤ þ0.9. Our results span orbits of Boyer-Lindquist
coordinate radii 4 ≤ r=M ≤ 30; notably, we investigate the strong-field regime, in some cases even
beyond the last-stable-orbit. We compare our numerical results for the gravitational wave fluxes with the
2.5th order accurate post-Newtonian (PN) prediction obtained analytically by Tanaka et al. [Phys. Rev. D
54, 3762 (1996)]: we find an unambiguous trend of the PN-prediction toward the numerical results when r
is large. At r=M ¼ 30 the fractional agreement between the full numerical flux, approximated as the sum
over the modes m ¼ 1, 2, 3, and the PN prediction is ≲0.5% in all cases tested. This is close to our
fractional numerical accuracy (∼0.2%). For smaller radii, the agreement between the 2.5PN prediction and
the numerical result progressively deteriorates, as expected. Our numerical data will be essential to develop
suitably resummed expressions of PN-analytical fluxes in order to improve their accuracy in the strongfield
regime.