Related papers: Hot Subdwarfs from the Stable Roche Lobe Overflow …
Recent discoveries from red optical proper motion and wide-field near-infrared surveys have uncovered a new population of ultracool subdwarfs -- metal-poor stars and brown dwarfs extending into the late-type M, L and possibly T spectral…
We review the current state of observational work on the formation of brown dwarfs, focusing on their initial mass function, velocity and spatial distributions at birth, multiplicity, accretion, and circumstellar disks. The available…
Hot subdwarf B stars (sdBs) are helium-burning stars with thin hydrogen-rich envelopes. Their most widely accepted formation channels involve binary evolution and progenitors near the tip of the red giant branch, thus studying these objects…
Many classical Be stars acquire their very rapid rotation by mass and angular-momentum transfer in massive binaries. Short-lived intermediate-phase objects have only been discovered recently. Data archives and the literature have been…
Virtually all binaries consisting of a white dwarf with a non-degenerate companion can be classified as either close post-interaction systems (with orbital periods of a few days or less), or wide systems (with periods longer than decades),…
We use both analytical analyses and numerical simulations to examine the evolution of residual gas within tidally-limited dwarf galaxies and globular clusters. If the gas sound speed exceeds about 10% of the central velocity dispersion, as…
The observed late-type WC Wolf-Rayet stars (WC7-9) with low luminosity below $\rm \log L/L_{\odot} < 5.4$ in the HR diagram cannot be reproduced satisfactorily by the evolutionary track of single stars. The mass transfer due to Roche lobe…
We report the discovery of an extremely close white dwarf plus F dwarf main-sequence star in a 12 hour binary identified by combining data from the RAdial Velocity Experiment (RAVE) survey and the Galaxy Evolution Explorer (GALEX) survey. A…
A detailed analysis of halo white dwarf candidates is presented, which is based on model atmosphere fits to observed energy distributions built from photoelectric or photographic magnitudes. Most of the candidates identified in reduced…
We discuss the evolution of binaries with moderately high masses (about 10 - 30 solar masses), and with periods of about 3 - 300d, corresponding mostly to early Case B. These are usually thought to evolve either by reasonably conservative…
Binary black holes (BBHs) can form from the collapsed cores of isolated high-mass binary stars. The masses and spins of these BBHs are determined by the complicated interplay of phenomena such as tides, winds, accretion, common-envelope…
The binary systems consisting of a Be star and a white dwarf (BeWDs) are very interesting.They can originate from the binaries composed of a Be star and a subdwarf O or B star (BesdOBs), and they can merge into red giants via luminous red…
I will start by discussing the evolutionary status of the white dwarf *progenitors*, the hot UV bright stars. Observations of UIT-selected UV bright stars in globular clusters suggest that a high percentage of them manage to evolve from the…
Ca-rich transients (CRTs, 2005E-like supernovae) exhibit unusually strong Ca features during their nebular phase, and their distribution in their host galaxies indicates that they belong to a metal-poor old population. We carried out a…
We study the angular momentum evolution of binaries containing two white dwarfs which merge and become cool helium-rich supergiants. Our object is to compare predicted rotation velocities with observations of highly evolved stars believed…
The formation of brown dwarfs via encounters between proto-stars has been confirmed with high-resolution numerical simulations with a restricted treatment of the thermal conditions. The new results indicate that young brown dwarfs (BDs)…
Compact binaries containing hot subdwarfs and white dwarfs have the potential to evolve into a variety of explosive transients. These systems could also explain hypervelocity runaway stars such as US 708. We use the detailed binary…
Most stars are members of binaries, and the evolution of a star in a close binary system differs from that of an ioslated star due to the proximity of its companion star. The components in a binary system interact in many ways and binary…
Hot subdwarfs represent a poorly understood late phase of stellar evolution. While binary evolution plays an important role for B-subdwarfs (sdB), the origin of the He dominated O-subdwarfs (He-sdO) is unknown. We search for chemical…
The observed distribution of periods and mass ratios of Algols with a B type primary at birth was updated. Conservative evolution fails to produce the large fraction with a high mass ratio: i.e. q in [0.4-0.6]. Interacting binaries thus…