Related papers: Formation of a rapidly rotating classical Be-star …
Currently used model of spherical accretion onto a magnetized rotating neutron star encounters major difficulties in explaining the entry rate of accreting material into the stellar field and spin evolution of long-period X-ray pulsars.…
We consider the spin angular momentum evolution of the accreting components of Algol-type binary stars. In wider Algols the accretion is through a disc so that the accreted material can transfer enough angular momentum to the gainer that…
The origin of the spins of giant planets is an open question in astrophysics. As planets and stars accrete from discs, if the specific angular momentum accreted corresponds to that of a Keplerian orbit at the surface of the object, it is…
During the mass-transfer phase in Algol systems, a large amount of mass and angular momentum are accreted by the gainer star which can be accelerated up to its critical Keplerian velocity. The fate of the gainer once it reaches this…
I review the process of mass transfer in a binary system through a stellar wind, with an emphasis on systems containing a red giant. I show how wind accretion in a binary system is different from the usually assumed Bondi-Hoyle…
One of the most mysterious astrophysical states is the common envelope (CE) phase of binary evolution, in which two stars are enshrouded by the envelope shed by one of them. Interactions between the stars and the envelope shrinks the orbit.…
The formation of binary stars is highly influenced by magnetic fields, which play a crucial role in transporting angular momentum. We conducted three-dimensional numerical simulations of binary star accretion via a circumbinary disk, taking…
The majority of massive stars reside in binary systems, which are expected to experience mass transfer during their evolution. However, so far the conditions under which mass transfer leads to a common envelope, and thus possibly to a…
Results are presented on component masses and system angular momenta for over a hundred low-temperature contact binaries. It is found that the secondary components in close binary systems are very similar in mass. Our observational evidence…
Most massive stars are born in binaries close enough for mass transfer episodes. These modify the appearance, structure, and future evolution of both stars. We compute the evolution of a 100-day period binary consisting initially of a 25 M…
Stars are generally spherical, yet their gaseous envelopes often appear non-spherical when ejected near the end of their lives. This quirk is most notable during the planetary nebula phase when these envelopes become ionized. Interactions…
High rates of stable mass transfer likely occur for some binary star systems, but the resulting flow of mass and angular momentum (AM) is unclear. We perform hydrodynamical simulations of a polytropic donor star and a point mass secondary…
Accreting main-sequence stars expand significantly when the mass accretion timescale is much shorter than their thermal timescales. This occurs during mass transfer from an evolved giant star onto a main-sequence companion in a binary…
The slow rotation of some young stars and the extreme rotation periods of some Ap stars have so far defied explanation. The absence of sufficiently efficient braking mechanisms for newly formed stars points to the star formation process…
Most major planetary bodies in the solar system rotate in the same direction as their orbital motion: their spin is prograde. Theoretical studies to explain the direction as well as the magnitude of the spin vector have had mixed success.…
A neutron star in binary orbit with a low-mass non-degenerate companion becomes a source of x-rays with millisecond variability when mass accretion spins it up. Centrifugally driven changes in density profile may initiate a phase transition…
Binary evolution plays a central role in producing rapidly rotating stars. Previous studies have shown that mass gainers in binaries can reach critical rotation after accreting only modest amounts of material, particularly during…
Close-orbit binaries consisting of two compact objects are a center of attention because of the detection of gravitational-radiation-induced mergers. The creation of close, compact-object binaries involves physical processes that are not…
Motions of stars in close binary systems with a conservative mass exchange are examined. It is shown that Paczynski-Huang model widely used now for obtaining the semi-major axis variation of a relative stars orbit is incorrect, because it…
Our current understanding of the physical processes of star formation is reviewed, with emphasis on processes occurring in molecular clouds like those observed nearby. The dense cores of these clouds are predicted to undergo gravitational…