Tidal breakup of binary stars at the Galactic Center. II. Hydrodynamic simulations - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado

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Abstract: In Paper I, we followed the evolution of binary stars as they orbited nearthe supermassive black hole SMBH at the Galactic center, noting the cases inwhich the two stars would come close enough together to collide. In this paperwe replace the point-mass stars by fluid realizations, and use asmoothed-particle hydrodynamics SPH code to follow the close interactions. Wemodel the binary components as main-sequence stars with initial masses of 1, 3and 6 Solar masses, and with chemical composition profiles taken from stellarevolution codes. Outcomes of the close interactions include mergers, collisionsthat leave both stars intact, and ejection of one star at high velocityaccompanied by capture of the other star into a tight orbit around the SMBH.For the first time, we follow the evolution of the collision products for many$\gtrsim 100$ orbits around the SMBH. Stars that are initially too small tobe tidally disrupted by the SMBH can be puffed up by close encounters orcollisions, with the result that tidal stripping occurs in subsequent periapsepassages. In these cases, mass loss occurs episodically, sometimes for hundredsof orbits before the star is completely disrupted. Repeated tidal flares, ofeither increasing or decreasing intensity, are a predicted consequence. Incollisions involving a low-mass and a high-mass star, the merger productacquires a high core hydrogen abundance from the smaller star, effectivelyresetting the nuclear evolution -clock- to a younger age. Elements like Li, Beand B that can exist only in the outermost envelope of a star are severelydepleted due to envelope ejection during collisions and due to tidal forcesfrom the SMBH. In the absence of collisions, tidal spin-up of stars is onlyimportant in a narrow range of periapse distances, $r t-2\lesssim r per\lesssim r t$ with $r t$ the tidal disruption radius.

Autor: Fabio Antonini, James C. Lombardi, David Merritt

Fuente: https://arxiv.org/

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