The sdB star KPD 0422+5421 was discovered to be a single-lined spectroscopic binary with a period of P = 0.0901795± (3×10) days (2 hours, 10 minutes). The U and B light curves display an ellipsoidal modulation with amplitudes of ≈ 0.02 magnitudes. The sdB star contributes nearly all of the observed flux. This and the absence of any reflection effect suggest that the unseen companion star is sma...

As a promising channel to Type Ia supernovae (SNe Ia), we have proposed a symbiotic binary system consisting of a white dwarf (WD) and a low mass red-giant (RG), where strong winds from the accreting WD play a key role to increase the WD mass to the Chandrasekhar mass limit. However, the occurrence frequency of SNe Ia through this channel has been still controversial. Here we propose two new ev...

Abstract: We present equations governing the way in which both the orbit and the intrinsic spins of stars in a close binary should evolve subject to a number of perturbing forces, including the effect of a third body in a possibly inclined wider orbit. We illustrate the solutions in some binary-star and triple-star situations: tidal friction in a wide but eccentric orbit of a radio pulsar about...

We study the circumstances under which first collisions occur in young and dense star clusters. The initial conditions for our direct N-body simulations are chosen such that the clusters experience core collapse within a few million years, before the most massive stars have left the main-sequence. It turns out that the first collision is typically driven by the most massive stars in the cluster...

We study the circumstances under which first collisions occur in young and dense star clusters. The initial conditions for our direct N-body simulations are chosen such that the clusters experience core collapse within a few million years, before the most massive stars have left the main-sequence. It turns out that the first collision is typically driven by the most massive stars in the cluster...

We use high-resolution Hubble Space Telescope imaging observations of the young (∼ 15 − 25 Myr) star cluster NGC 1818 in the Large Magellanic Cloud to derive an estimate for the binary fraction of F stars (1.3 < M⋆/M⊙ < 1.6). This study provides the strongest constraints yet on the binary fraction in a young star cluster in a low-metallicity environment ([Fe/H] ∼ −0.4). Employing artificial sta...

Aims. We report on the discovery of J0644+3344, a bright deeply eclipsing cataclysmic variable (CV) binary. Methods. Optical photometric and spectroscopic observations were obtained to determine the nature and characteristics of this CV. Results. Spectral signatures of both binary components and an accretion disk can be seen at optical wavelengths. The optical spectrum shows broad H I, He I, an...

Three-body effects greatly complicate stellar evolution. We model the effects of encounters of binaries with single stars, based on parameters chosen from conditions prevalent in the cores of globular clusters. For our three-body encounters, we start with a population of primordial binaries, and choose incoming stars from the evolving single star populations of paper I. In addition, we study th...

Binary F stars exhibit large brightness anomaly, which is defined here as the difference between the absolute magnitude from the uvby photometry and the actual absolute magnitude of the star. We have found that the anomaly inversely correlates with the binary components separation. There is evidence that the correlation reflects actual population differences between close and wide binary pairs,...