D. Mancieri, L. Broggi, M. Vinciguerra, A. Sesana, and M. Bonetti We present realistic eccentricity distributions for extreme mass ratio inspirals (EMRIs) forming via the two-body relaxation channel in nuclear star clusters, tracking their evolution up to the final plunge onto the central Schwarzschild massive black hole (MBH). We find that EMRIs can retain significant eccentricities at plunge, with a distribution peaking at \(e_\mathrm{pl}≈0.2\), and a considerable fraction reaching much higher values.

M. Toscani, L. Broggi, A. Sesana, and E. M. Rossi In this paper, we investigate the gravitational wave (GW) emission from stars tidally disrupted by black holes (TDEs), using a semi- analytical approach. Contrary to previous works where this signal is modeled as a monochromatic burst, we here take into account all its harmonic components. On top of this, we also extend the analysis to a population of repeated-partial TDEs, where the star undergoes multiple passages around the black hole before complete disruption.

Broggi, Luca In this Letter, we present a new formulation of loss cone theory as a reaction-diffusion system, which accounts for loss cone events through a sink term and can be orbit-averaged. It can recover the standard approach based on boundary conditions, and is derived from a simple physical model that overcomes many of the classical theoretical constraints. We test our formulation by computing the relaxed distribution of disruptive orbits in phase space, that has a simple analytic form and agrees with the pericentre of tidal disruption events at disruption predicted by non-averaged models.

Mancieri, Davide; Broggi, Luca; Bonetti, Matteo; Sesana, Alberto Extreme mass ratio inspirals (EMRIs) are anticipated to be primary gravitational wave sources for the Laser Interferometer Space Antenna (LISA). They form in dense nuclear clusters, when a compact object is captured by the central massive black holes (MBHs) as a consequence of the frequent two-body interactions occurring between orbiting objects. The physics of this process is complex and requires detailed statistical modeling of a multi-body relativistic system.

Broggi, Luca; Stone, Nicholas C.; Ryu, Taeho; Bortolas, Elisa; Dotti, Massimo; Bonetti, Matteo; Sesana, Alberto Two-body relaxation may drive stars onto near-radial orbits around a massive black hole, resulting in a tidal disruption event (TDE). In some circumstances, stars are unlikely to undergo a single terminal disruption, but rather to have a sequence of many grazing encounters with the black hole. It has long been unclear what is the physical outcome of this sequence: each of these encounters can only liberate a small amount of stellar mass, but may significantly alter the orbit of the star.

Polkas, Markos; Bonoli, Silvia; Bortolas, Elisa; Izquierdo-Villalba, David; Sesana, Alberto; Broggi, Luca; Hoyer, Nils; Spinoso, Daniele Stars can be ripped apart by tidal forces in the vicinity of a massive black hole, causing luminous flares classified as tidal disruption events (TDEs). These events could be contributing to the mass growth of intermediate-mass black holes, while new samples from ongoing transient surveys can provide useful information on this unexplored growth channel.

Bondani, Stefano; Bonetti, Matteo; Broggi, Luca; Haardt, Francesco; Sesana, Alberto; Dotti, Massimo. Primordial black holes (PBH), supposedly formed in the very early Universe, have been proposed as a possible viable dark matter candidate. In this work we characterize the expected gravitational wave (GW) losses from a population of PBHs orbiting Sgr A⋆, the super-massive black hole at the Galactic center, and assess the signal detectability by the planned space-borne interferometer LISA and by the proposed next generation space-borne interferometer μAres.

Bortolas, Elisa; Ryu, Taeho; Broggi, Luca; Sesana, Alberto. Tidal disruption events (TDEs) of stars operated by massive black holes (MBHs) will be detected in thousands by upcoming facilities such as the Vera Rubin Observatory. In this work, we assess the rates of standard total TDEs, destroying the entire star, and partial TDEs, in which a stellar remnant survives the interaction, by solving 1-D Fokker-Planck equations. Our rate estimates are based on a novel definition of the loss cone whose size is commensurate to the largest radius at which partial disruptions can occur, as motivated by relativistic hydrodynamical simulations.

Broggi, Luca; Bortolas, Elisa; Bonetti, Matteo; Sesana, Alberto; Dotti, Massimo. In this paper, we develop a computationally efficient, two-population, time-dependent Fokker–Plank approach in the two dimensions of energy and angular momentum to study the rates of tidal disruption events (TDEs), extreme mass ratio inspirals (EMRIs), and direct plunges occurring around massive black holes (MBHs) in galactic nuclei. We test our code by exploring a wide range of the astrophysically relevant parameter space, including MBH masses, galaxy central densities, and inner density slopes.