Recent observations of PSR J0045-7319, a radio pulsar in a close eccentric orbit with a massive B-star companion, indicate that the system's orbital period is decreasing on a timescale of 5 10 years, which is much shorter than the timescale of 10 years given by the standard theory of tidal dissipation in radiative stars. Observations also provide strong evidence that the B-star is rotating rapi...

Recent observations of PSR J0045-7319, a radio pulsar in a close eccentric orbit with a massive B-star companion, indicate that the system's orbital period is decreasing on a timescale of ≈ 5 × 10 5 years, which is much shorter than the timescale of ≈ 10 9 years given by the standard theory of tidal dissipation in radiative stars. Observations also provide strong evidence that the B-star is rot...

Massive stars rapidly change their masses through strong stellar winds and mass transfer in binary systems. The latter aspect is important for populations of massive stars as more than 70% of all O-stars are expected to interact with a binary companion during their lifetime. We show that such mass changes leave characteristic signatures in stellar mass functions of young star clusters which can...

RZ Cas is an Algol-type partial eclipsing binary, the secondary component of which has filled its Roche lobe. Its visual magnitude is 6.18 and its period is 1.195 days. The most important characteristics of RZ Cas are period change (due to mass transfer) and anomalies in the primary minimum of its light curve (due to δ Scuti pulsations). In this paper, light curves of RZ Cas are obtained using ...

An accretion disc around a compact star in a close binary star system is an ubiquitous and essential object. Accretion discs play, for example, important roles in cataclysmic variables, nova and X-ray sources. The standard theory to explain the physics in accretion discs is the α-disc model proposed by Shakura and Sunyaev (1973). In this theory, the accretion disc is in some kind of turbulent s...

We present a detailed determination of the astrophysical parameters of the chromospherically active binary star EI Eridani. Our new radial velocities allow to improve the set of orbital elements and reveal long-term variations of the barycentric velocity. A possible third-body orbit with a period of ≈ 19 years is presented. Absolute parameters are determined in combination with the Hipparcos pa...

Following merger, a neutron star (NS) binary can produce roughly one of three different outcomes: (1) a stable NS, (2) a black hole (BH), or (3) a supra-massive, rotationally-supported NS, which then collapses to a BH following angular momentum losses. Which of these fates occur and in what proportion has important implications for the electromagnetic transient associated with the mergers and t...

We compute and present the distribution in mass of single and binary neutron stars, strange stars, and black holes. The calculations were performed using a stellar population synthesis code. We follow all phases of single and binary evolution, starting from a ZAMS binary and ending in the creation of one compact object (neutron star, black hole, strange star) and a white dwarf, or two compact o...

We describe a method of determining the system parameters in non-eclipsing interacting binaries. We find that the extent to which an observer sees the shape of the Roche-lobe of the secondary star governs the amount of distortion of the absorption line profiles. The width and degree of asymmetry of the phase-resolved absorption line profiles show a characteristic shape, which depends primarily ...

We discuss how rotation and binary interactions may be related to the diversity of type Ibc supernovae and long gamma-ray bursts. After presenting recent evolutionary models of massive single and binary stars including rotation, the Tayler-Spruit dynamo and binary interactions, we argue that the nature of SNe Ibc progenitors from binary systems may not significantly differ from that of single s...