Showing papers in "Astronomy Letters in 1998"

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

Abstract: We analyze the effect of the quadrupole component in the mass distribution of a rapidly rotating neutron star on energy release in the boundary layer on the surface of the accreting star and in the accretion disk in the cases where the stellar radius is smaller (or larger) than the radius of the marginally stable circular orbit. We calculate the velocities and trajectories of the particles that fall on the stellar surface from the marginally stable orbit for a low- luminosity accreting source. The corresponding external gravitational field of the star is modeled by a new exact solution of the Einstein equations in vacuum. The parameters of this solution are adjusted by reconciling the numerical data for the radius of the marginally stable orbit and the gravitational redshift of Cook et al. (1994) with the corresponding data in the analytical solution. For various equations of state, we consider 1.4 solar mass normal sequences and maximum mass normal sequences.

New spectroscopic components in six multiple systems

Abstract: New close sub-systems are discovered in 8 visual late-type double stars. Elements of spectroscopic orbits (4 double-lined and 4 single-lined) are given for the components of quadruple systems ADS 1134 and 11163, for the components of triple systems ADS 455, 497, 5436, 8236, 10044, and for the primary of the optical pair ADS 9444. Magnitudes, colors, spectral types, masses of individual components are estimated by combining all available data with Hipparcos parallaxes. Among these stellar systems we note a subdwarf triple ADS 497, an old system with subgiant components ADS 10044, and a visual triple ADS 11163 with additional very low mass (possibly substellar) spectroscopic companion in a 4.6 day orbit. The astrometric orbit of ADS 8236B with a semimajor axis of 30 mas and a period of 4.6 yr may be recoverable from Hipparcos data.