4 research outputs found
Accretion into black holes with magnetic fields, and relativistic jets
We discuss the problem of the formation of a large-scale magnetic field in
the accretion disks around black holes, taking into account the non-uniform
vertical structure of the disk. The high electrical conductivity of the outer
layers of the disk prevents the outward diffusion of the magnetic field. This
implies a stationary state with a strong magnetic field in the inner parts of
the accretion disk close to the black hole, and zero radial velocity at the
surface of the disk. Structure of advective accretion disks is investigated,
and conditions for formation of optically thin regions in central parts of the
accretion disk are found. The problem of jet collimation by magneto-torsion
oscillations is considered.Comment: 6 pages, 4 figure
Time delay between the optical and X-ray outbursts in the high mass X-ray transient A0535+26/HDE245770
The optical behaviour of the Be star in the high mass X-ray transient
A0535+26/HDE245770 shows that at the periastron typically there is an
enhancement in the luminosity of order 0.02 to few tenths mag, and the X-ray
outburst happens about 8 days after the periastron. We construct a quantitative
model of this event, basing on the a nonstationary accretion disk behavior,
connected with a high ellipticity of the orbital motion. The ephemeris used in
this paper -- JD = JD(2,444,944) n(111.0 0.4)
days are derived from the orbital period of the system P days, determined by Priedhorsky & Terrell (1983), and from the optical
flare of December 5, 1981 (Giovannelli et al., 1985) (here after 811205-E; E
stands for the Event occurred at that date) that triggered the subsequent X-ray
outburst of December 13, 1981 (Nagase et al., 1982) (here after 811213-E). We
explain the observed time delay between the peaks of the optical and X-ray
outbursts in this system by the time of radial motion of the matter in the
accretion disk, after an increase of the mass flux in the vicinity of a
periastral point in the binary. This time is determined by the turbulent
viscosity, with the parameter . The increase of the mass flux
is a sort of flush that reaches the external part of the accretion disk around
the neutron star, producing an enhancement in the optical luminosity. The
consequent X-ray flare happens when the matter reaches the hot central parts of
the accretion disk, and the neutron star surface.Comment: 30 pages, 15 figures, with correction in abstrac