Many, possibly most, stars form in binary and higher order multiple systems. Therefore, the properties and frequency of binary systems provide strong clues to the star-formation process, and constraints on star-formation models. However, the majority of stars also form in star clusters in which the birth binary properties and frequency can be altered rapidly by dynamical processing. Thus, we al...

The shape of a rotating star consisting of equilibrium plasma is considered. The velocity of apsidal rotation of close binary stars (pe-riastron rotation) which depends on the star shapes is calculated. The obtained estimations are in a good agreement with the observation data of the apsidal motion in binary systems.

Compared to earlier studies on the subject, we use results of intermediate mass case B close binary evolution computed with updated data, to predict the population of B-type accretion stars for different regions of star formation, in the Galaxy and in the Magellanic Clouds. We will make a distinction between accretion stars with a (helium burning) subdwarf, respectively white dwarf and neutron ...

Most stars reside in binary/multiple star systems; however, previous models of planet formation have studied growth of bodies orbiting an isolated single star. Disk material has been observed around both components of some young close binary star systems. Additionally, it has been shown that if planets form at the right places within such disks, they can remain dynamically stable for very long ...

We report the discovery of an eclipsing X-ray binary with a 3.62-hr period within 24 of the center of the dwarf starburst galaxy NGC 4214. The orbital period places interesting constraints on the nature of the binary, and allows for a few very different interpretations. The most likely possibility is that the source lies within NGC 4214 and has an X-ray luminosity, Lx, of up to 7 × 10 ergs s. I...