Dynamical friction in slab geometries and accretion discs

Abstract

The evolution of planets, stars and even galaxies is driven, to a large extent, by dynamical friction of gravitational origin. There is now a good understanding of the friction produced by extended media, either collisionless of fluid-like. However, the physics of accretion or protoplanetary disks, for instance, is described by slab-like geometries instead, compact in one spatial direction. Here, we find, for the first time, the gravitational wake due to a massive perturber moving through a slab-like medium, describing e.g. accretion disks with sharp transitions. We show that dynamical friction in such environments can be substantially reduced relatively to spatially extended profiles. Finally, we provide simple and accurate expressions for the gravitational drag force felt by the perturber, in both the subsonic and supersonic regime.

Constraints on the astrophysical environment of binaries with gravitational-wave observations

“…Dynamical friction was treated at the nonrelativistic level and neglecting effects of the geometry of the environment. Such effects may be important for thin accretion disks, for example, but the generalization of the results of Vicente et al (2019) regarding circular motion is still missing. Possible multiband detections were not explored here, but they will improve the bound we discussed even further.…”

“…Our results show a very mild dependence on the exact value of r min . There are special-relativistic corrections to this formula (Barausse 2007), and corrections for slab-like geometries (such as those in accretion disks) (Vicente et al 2019). We do not consider these effects here.…”

“…The geometry of the environment, on the other hand, may be relevant for thin accretion disks. When the motion is supersonic, geometry may suppress friction by a factor two (Vicente et al 2019). Suppression is stronger for subsonic motion.…”

Drifting through the medium: kicks and self-propulsion of binaries within accretion disks and other environments

“…Here, we are instead interested in the CM motion induced by interaction with the environment, in particular through dynamical friction. Such interaction has been explored, and is known to drive the inspiral faster, providing clear smoking-gun signatures of nontrivial astrophysical environments via gravitational-wave tracking of the rate of inspiral (Macedo et al 2013; Barausse et al 2014;Vicente et al 2019;Cardoso & Maselli 2019). What happens to the CM of the binary as it evolves under dynamical friction and accretion?…”

Stirred and shaken: Dynamical behavior of boson stars and dark matter cores

“…Treating perturbers as pointlike is a successful and standard tool in BH perturbation theory [40][41][42], in seismology [43] or in calculations of gravitational drag by fluids [44,45]. In this approximation one loses smallscale information.…”