Fake plunges are very eccentric real EMRIs in disguise

Abstract

Abstract. The capture of a compact object in a galactic nucleus by a massive black hole (MBH) is the best way to map space and time around it. Compact objects such as stellar black holes on a capture orbit with a very high eccentricity have been wrongly assumed to be lost for the system after an intense burst of radiation, which has been described as a "direct plunge". We prove that these very eccentric capture orbits spend actually a similar number of cycles in a LISA-like detector as those with lower eccentricities if the central MBH is spinning. Although the rates are higher for high-eccentricity EMRIs, the spin also enhances the rates of lower-eccentricity EMRIs. This last kind have received more attention because of the fact that higheccentricity EMRIs were thought to be direct plunges and thus negligible. On the other hand, recent work on stellar dynamics has demonstrated that there seems to be a complot in phase space acting on these lower-eccentricity captures, since their rates decrease significantly by the presence of a blockade in the rate at which orbital angular momenta change takes place. This socalled "Schwarzschild barrier" is a result of the impact of relativistic precession on to the stellar potential torques, and thus it affects the enhancement on lower-eccentricity EMRIs that one would expect from resonant relaxation. We confirm and quantify the existence of this barrier using a statitical sample of 2,500 direct-summation N−body simulations using both a post-Newtonian but also, and for the first time, a geodesic approximation for the relativistic orbits. The existence of the barrier prevents "traditional EMRIs" from approaching the central MBH, but if the central MBH is spinning the rate will be anyway dominated by highlyeccentric extreme-mass ratio inspirals, which insolently ignore the presence of the barrier, because they are driven by two-body relaxation.

Relativistic mergers of black hole binaries have large, similar masses, low spins and are circular

“…The first implementation of relativistic terms in a dynamical code was done by one of us and they have been well tested in a number of different works that feature different orders in the expansion (see e.g. Kupi et al 2006;Amaro-Seoane et al 2012;Brem et al 2013Brem et al , 2014Antognini et al 2014).…”

EMRI Data Analysis with a Phenomenological Waveform

“…In general, the deviations from Kerr could come in several ways: (i) it is Kerr BH but there is an additional perturber (gas disk, another MBH) (ii) it is not Kerr BH but some other object satisfying GR (boson star, gravastar), (iii) there are deviations from GR. For discussion on the topics we refer the reader to [3][4][5] and references therein.…”