The Disc Accretion in Gravitational Field of a Rapidly Rotating Neutron\n Star with a Rotationally Induced Quadrupole Mass Distribution

Abstract

We analyze the effect of the quadrupole component in the mass distribution of\na rapidly rotating neutron star on energy release in the boundary layer on the\nsurface of the accreting star and in the accretion disk in the cases where the\nstellar radius is smaller (or larger) than the radius of the marginally stable\ncircular orbit. We calculate the velocities and trajectories of the particles\nthat fall on the stellar surface from the marginally stable orbit for a low-\nluminosity accreting source. The corresponding external gravitational field of\nthe star is modeled by a new exact solution of the Einstein equations in\nvacuum. The parameters of this solution are adjusted by reconciling the\nnumerical data for the radius of the marginally stable orbit and the\ngravitational redshift of Cook et al. (1994) with the corresponding data in the\nanalytical solution. For various equations of state, we consider 1.4 solar mass\nnormal sequences and maximum mass normal sequences.\n