Viscous effects on the interaction between the coplanar decretion disc and the neutron star in Be/X-ray binaries

By A. Okazaki, Matthew R. Bate, Gordon I. Ogilvie, J. E. Pringle. 2002

137 citations recorded by the source corpus.

We study the viscous effects on the interaction between the coplanar Be-star disc and the neutron star in Be/X-ray binaries, using a three-dimensional, smoothed particle hydrodynamics code. For simplicity, we assume the Be disc to be isothermal at the temperature of half the stellar effective temperature. In order to mimic the gas ejection process from the Be star, we inject particles with the Keplerian rotation velocity at a radius just outside the star. Both the Be star and the neutron star are treated as point masses. We find that the Be-star disc is effectively truncated if the Shakura‐Sunyaev viscosity parameter αSS � 1, which confirms the previous semi-analytical result. In the truncated disc, the material decreted from the Be star accumulates, so that the disc becomes denser more rapidly than if around an isolated Be star. The resonant truncation of the Be disc results in a significant reduction of the amount of gas captured by the neutron star and a strong dependence of the mass-capture rate on the orbital phase. We also find that an eccentric mode is excited in the Be disc through direct driving as a result of a one-armed bar potential of the binary. The strength of the mode becomes greater in the case of a smaller viscosity. In a high-resolution simulation with αSS = 0.1, the eccentric mode is found to precess in a prograde sense. The mass-capture rate by the neutron star modulates as the mode precesses.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5688536cb2d74a5776eeea01d8b1cbbb8319ad76

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Citations in the corpus

Classical Be stars (2013, background): “Additionally, in the models by Okazaki et al. (2002), a tightly folded spiral structure in the inner disk arises, triggered at periastron.”
Finite, Intense Accretion Bursts from Tidal Disruption of Stars on Bound Orbits (2012, methodology): “The code is based on a version originally developed by Benz (1990); Benz et al. (1990); Bate et al. (1995) and has been extensively used by many papers (e.g., Okazaki et al. (2002); Hayasaki et al. (2007)).”
Be/X-ray binaries (2011, background): “…data sample is shown with a solid line, while the dashed line represents a power-law fit with exponent n=4/3. point of view and the theory subsequently developed by Okazaki and collaborators in a series of papers: Negueruela & Okazaki (2001); Okazaki & Negueruela (2001); Okazaki et al. (2002).”