Showing papers in "Astronomy and Astrophysics in 1972"

Accretion Disc Models for Compact X-Ray Sources

Abstract: The accretion process is considered, in cases when the infalling matter possesses angular momentum and forms a disc spinning around a central compact mass. This situation occurs when gas falls onto a black hole or neutron star from a binary companion, and may be relevant to galactic X-ray sources. The spectrum of the radiation emitted by gas spiralling down into a black hole is calculated and compared with the data on Cygnus X-1. Rapid irregular variability is expected in this model. If the compact object is a neutron star, the gas dynamics near the star may be controlled by the stellar magnetic field. The main X-ray emission then comes not from the disc, but from regions on the stellar surface near the magnetic poles. An interpretation of Centaurus X-3 involving a rotating magnetized neutron star is proposed. It is emphasized that accretion discs can display a wide range of properties (depending on the accretion rate, viscosity, etc.). Tentative interpretation of some other phenomena are also proposed.