Related papers: Non-standard modeling of a possible blue straggler…
The two-dimensional internal rotation of KIC11145123 has been inferred via asteroseismology. Based on the Optimally Localized Averaging method and a simple three-zone modeling of the internal rotation, we have found evidence for a contrast…
A spectroscopic analysis was carried out to clarify the properties of KIC 11145123 -- the first main-sequence star with a determination of core-to-surface rotation -- based on spectra observed with the High Dispersion Spectrograph (HDS) of…
Observations from the Kepler satellite were recently published for three bright G-type stars, which were monitored during the first 33.5d of science operations. One of these stars, KIC 11026764, exhibits a characteristic pattern of…
Optical spectroscopy of the blue star KIC 10449976 shows that it is an extremely helium-rich subdwarf with effective temperature T=40000+/-300 K and surface gravity log g=5.3+/-0.1. Radial-velocity measurements over a five-day timescale…
The frequency ratios $r_{01}$ and $r_{10}$ of KIC 11081729 decrease firstly and then increase with the increase in frequency. For different spectroscopic constraints, all models with overshooting parameter $\delta_{\mathrm{ov}}$ less than…
In the overshoot mixing model with an exponentially decreasing diffusion coefficient, the initial value of the diffusion coefficient plays a crucial role. According to the turbulent convective mixing model, the characteristic length of…
By using the high resolution spectrograph FLAMES@VLT we performed the first systematic campaign devoted to measure chemical abundances of blue straggler stars (BSSs). These stars, whose existence is not predicted by the canonical stellar…
Main-sequence stars with convective envelopes often appear larger and cooler than predicted by standard models of stellar evolution for their measured masses. This is believed to be caused by stellar activity. In a recent study, accurate…
This paper reports the discovery of an Algol system KIC 10736223 that just past the rapid mass transfer stage. From the light curve and radial-velocity modelling we find KIC 10736223 to be a detached Algol system with the less-massive…
The physical parameters of the retired A star HD 185351 were analysed in great detail by Johnson et al. (2014) using interferometry, spectroscopy and asteroseismology. Results from all independent methods are consistent with HD 185351…
Yellow straggler stars (YSSs) fall above the subgiant branch in optical color-magnitude diagrams, between the blue stragglers and the red giants. YSSs may represent a population of evolved blue stragglers, but none have the direct and…
Motivated by the WMAP results indicating an early epoch of reionization, we consider alternative cosmic star formation models which are capable of reionizing the early intergalactic medium. We develop models which include an early burst of…
KIC 10661783 is an eclipsing binary that shows Delta Sct-like oscillations. More than 60 pulsation frequencies have been detected in its light curve as observed by the Kepler satellite. We want to determine the fundamental stellar and…
With the equivalent area of a 16m telescope, ESPRESSO in 4UT mode allows to inaugurate high resolution spectroscopy for solar-type stars belonging to extragalactic globular clusters. We determine the chemical composition of an extragalactic…
Asteroseismology provides a direct observational window into the structure and evolution of stars. While spectroscopic and photometric methods only provide information about the surface properties of stars, asteroseismology, through the…
KIC 10526294 is a very slowly rotating and slowly pulsating late B-type star. Its 19 consecutive dipole gravity modes constitute a series with almost constant period spacing. This unique collection of identified modes probes the near-core…
Convective overshoot mixing is a critical ingredient of stellar structure models, but is treated in most cases by ad hoc extensions of the mixing-length theory for convection. Advanced theories which are both more physical and numerically…
It has been known for several decades that transport of chemical elements is induced by the process of microscopic atomic diffusion. Yet, the effect of atomic diffusion, including radiative levitation, has hardly been studied in the context…
We have performed evolutionary calculations of very-low-mass stars from 0.08 to 0.8 $\msol$ for different metallicites from [M/H]= -2.0 to -1.0 and we have tabulated the mechanical, thermal and photometric characteristics of these models.…
The goal of stellar evolution theory is to predict the structure of stars throughout their lifetimes. Usually, these predictions can be assessed only indirectly, for example by comparing predicted and observed effective temperatures and…