Three-dimensional hydrodynamical simulations of colliding stars . III - Collisions and tidal captures of unequal-mass main-sequence stars

• Published in: The Astrophysical journal Vol. 389; no. 2; pp. 546 - 557
• Main Authors: Benz, W., Hills, J. G.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS University of Chicago Press 01.04.1992
• Subjects: Astronomy; Astrophysics; BASIC INTERACTIONS; BINARY STARS; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COMPUTERIZED SIMULATION; Earth, ocean, space; Exact sciences and technology; FLUID MECHANICS; GRAVITATIONAL INTERACTIONS; HYDRODYNAMICS; INTERACTIONS; ITERATIVE METHODS; MAIN SEQUENCE STARS; MASS; MECHANICS; NUMERICAL SOLUTION; RUNGE-KUTTA METHOD; SIMULATION; STAR CLUSTERS; STARS 661300 > Other Aspects of Physical Science > (1992-); Stellar dynamics and kinematics; Stellar systems. Galactic and extragalactic objects and systems. The universe; THREE-DIMENSIONAL CALCULATIONS; Three dimensional model; Head on collision; Close encounter; Globular cluster; Hydrodynamic model; Numerical simulation; Stellar collision; Grazing collision; Stellar dynamics; Main sequence star; Celestial mechanics
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/171230

A 3D smooth-particle hydrodynamic code with 7000 particles is used to simulate collisions between lower main sequence (MS) stars whose masses differ by a factor of five. Collisions between point-mass intruders and MS stars are simulated to study how the physics of the encounters depends on the finite radius of the smaller MS stars. It is found that the two MS stars become gravitationally bound in a physical collision if their relative velocity at infinity is less than a critical velocity Vd. Vd decreases from 1000 km/s in a head-on collision to 150 km/s in a grazing one. If the less massive star is replaced by a point mass, Vd remains the same for grazing collision and tidal encounters but drops to about 600 km/s in head-on collisions. The collision and coalescence of two MS stars resets the nuclear clock of the coalesced star, so it contracts to the MS. Tidal capture of binary stars in globular clusters can only occur in encounters in which the closest approach of the two stars to their center of mass is less than 2.0 times the sum of their radii.