Related papers: Subdwarf B stars from the common envelope ejection…

The formation of hot subdwarf stars is still unclear. Both single-star and binary scenarios have been proposed to explain the properties of these evolved stars situated at the extreme blue end of the horizontal branch. The observational…

Blue hook stars are a class of subluminous extreme horizontal branch stars that were discovered in UV images of the massive globular clusters omega Cen and NGC 2808. These stars occupy a region of the HR diagram that is unexplained by…

We present FUSE spectra of three He-rich sdB stars. Two of these stars, PG1544+488 and JL87, reveal extremely strong C III lines, suggesting that they have mixed triple-alpha carbon from the deep interior out to their surfaces. Using TLUSTY…

In this study, we concentrate on the formation and evolution of hot subdwarfs binaries through the stable Roche lobe overflow (RLOF) channel of intermediate-mass binaries. We aim at setting out the properties of hot subdwarfs and their…

Subdwarf B (sdB) stars form the blue end of the horizonal branch (EHB). Their peculiar atmospheric abundance patterns are due to diffusion processes. However, diffusion models fail to explain these anomalies quantitatively. Weak mass loss…

We present the results of Monte Carlo mass-loss predictions for hot low-mass stars, specifically for Subdwarf B (SdB) stars. It is shown that the mass-loss rates on the Horizontal Branch (HB) computed from radiative line-driven wind models…

Hot subdwarf B (sdB) and O (sdO) type stars are evolved helium-burning objects that lost their hydrogen envelope before the helium flash when their progenitors were close to the tip of the red giant branch. They populate the extreme…

Hot subdwarf B stars (sdBs) are extreme horizontal branch stars believed to originate from close binary evolution. Indeed about half of the known sdB stars are found in close binaries with periods ranging from a few hours to a few days. The…

Binaries consisting of a hot subdwarf star and an accreting white dwarf (WD) are sources of gravitational wave radiation at low frequencies and possible progenitors of type Ia supernovae if the WD mass is large enough. Here, we report the…

A radial velocity follow-up of the long-period sdOB+G1V type spectroscopic binary SB 744 revealed strong lines of fluorine and lead in the optical spectrum of the sdOB star and subsolar metallicity in the G1V companion. With high-quality…

Due to orbital decay by gravitational-wave radiation, some close-binary helium white dwarfs are expected to merge within a Hubble time. The immediate merger products are believed to be helium-rich sdO stars, essentially helium main-sequence…

Helium-burning hot subdwarf stars of spectral types O and B (sdO/B) are thought to be produced through various types of binary interaction. The helium-rich hot subdwarf star EC22536-5304 was recently found to be extremely enriched in lead.…

Hot subdwarf-B (sdB) stars in long-period binaries are found to be on eccentric orbits, even though current binary-evolution theory predicts these objects to be circularised before the onset of Roche-lobe overflow (RLOF). To increase our…

Asteroseismology of non-radial pulsations in Hot B Subdwarfs (sdB stars) offers a unique view into the interior of core-helium-burning stars. Ground-based and space-borne high precision light curves allow for the analysis of pressure and…

Hot subdwarfs with close low-mass M-type or brown dwarf companions usually show the reflection effect and often also eclipses. Through inspecting the light variations, we estimate the fractions of reflection effect systems detected in…

We present the results of a spectral analysis of a large sample of subdwarf B stars selected from follow-up observations of candidates from the Hamburg Quasar Survey. Fundamental parameters (effective temperature, gravity, and helium…

Hot subdwarfs are core-helium burning stars that show lower masses and higher temperatures than canonical horizontal branch stars. They are believed to be formed when a red giant suffers an extreme mass-loss episode. Binary interaction is…

Double helium white dwarfs (He WDs) are one type of gravitational wave source and are greatly important in the studies of binary interaction, particularly in the common envelope (CE) ejection physics. Most double He WDs with mass ratios of…

We measured projected rotational velocities of more than a hundred apparently single sdBs. A comparison is made with sdB stars in binary systems with orbits so wide, that tidal interaction becomes negligible. All of these stars are slow…

Hot subdwarf stars (sdO/Bs) are evolved core helium-burning stars with very thin hydrogen envelopes, which can be formed by common envelope ejection. Close sdB binaries with massive white dwarf (WD) companions are potential progenitors of…