Related papers: Hot subluminous stars
We present synthetic spectra and SEDs computed along evolutionary tracks at Z=1/5 Zsun and Z=1/30 Zsun, for masses between 15 and 150 Msun. We predict that the most massive stars all start their evolution as O2 dwarfs at sub-solar…
We used FLAMES+GIRAFFE (Medusa mode) at the VLT to obtain moderately high resolution spectra for 30 red horizontal branch (RHB) stars, 4 RR Lyrae variables, and 17 blue horizontal branch (BHB) stars in the low-concentration, moderately…
In this study we present an analysis of a sample of field blue straggler (BS) stars that show high ultra violet emission in their spectral energy distributions (SED): indication of a hot white dwarf (WD) companion to BS. Using photometry…
Wide hot subdwarf B (sdB) binaries with main-sequence companions are outcomes of stable mass transfer from evolved red giants. The orbits of these binaries show a strong correlation between their orbital periods and mass ratios. The origins…
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 construct a speculative scenario for rotation-induced extra helium mixing to the envelope of horizontal branch (HB) stars. This scenario differs from previous ones in that the mixing occurs after the star has left the red giant branch…
We report the discovery of an eclipsing binary -- PTF1 J072456$+$125301-- composed of a subdwarf B (sdB) star ($g'=17.2^m$) with a faint companion. Subdwarf B stars are core helium-burning stars, which can be found on the extreme horizontal…
The origin of intermediate helium (He)-rich hot subdwarfs are still unclear. Previous studies have suggested that some surviving Type Ia supernovae (SNe Ia) companions from the white dwarf~+~main-sequence (WD+MS) channel may contribute to…
UV observations of some massive globular clusters uncovered a significant population of very hot stars below the hot end of the horizontal branch (HB), the so-called blue hook stars. This feature might be explained either as results of the…
The survey phase of the Kepler Mission includes a number of hot subdwarf B (sdB) stars to search for nonradial pulsations. We present our analysis of two sdB stars that are found to be g-mode pulsators of the V1093 Her class. These two…
We present an extensive survey for rapid pulsators among Extreme Horizontal Branch (EHB) stars in omega Cen. The observations performed consist of nearly 100 hours of time-series photometry, as well as low-resolution spectroscopy. We…
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…
Barium (Ba), CH, and extrinsic or Tc-poor S-type stars are evolved low- and intermediate-mass stars that show enhancement of slow-neutron-capture-process elements on their surface, an indication of mass accretion from a former asymptotic…
The evolution of low- and intermediate mass stars at the onset and during core helium burning is reviewed. Particular emphasis is laid on structural differences, which may allow to identify a star's nature and evolutionary phase in spite of…
We provide an observational view of evolutionary models in the Hertzsprung--Russell diagram, on the main sequence. For that we computed evolutionary models with the code STAREVOL for 15 < M/Msun < 100. We subsequently calculated atmosphere…
Using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, we have obtained deep far-ultraviolet images of the compact elliptical galaxy M32. When combined with earlier near-ultraviolet images of the same field, these…
We present evolutionary pathways for creating hot subdwarf OB (sdOB) stars from hierarchical triple configurations. We use the population synthesis code Multiple Stellar Evolution (MSE) to follow the stellar, binary, and gravitational…
There is growing evidence that some Be stars were spun up through mass transfer in a close binary system, leaving the former mass donor star as a hot, stripped-down object. There are five known cases of Be stars with hot subdwarf (sdO)…
Blue straggler stars are unique main-sequence stars that appear more luminous, hotter, and therefore younger, than their coeval counterparts. In star clusters, these stars are located above the cluster turn-off in the Hertzsprung-Russell…
Recent UV observations of the globular cluster NGC2808 (Brown et al. 2001) show a significant population of hot stars fainter than the zero-age horizontal branch (``blue hook'' stars), which cannot be explained by canonical stellar…