Related papers: Chemically peculiar stars and their temperature ca…
One of the very first steps astronomers working in stellar physics perform to advance in their studies, is to determine the most common/relevant physical parameters of the objects of study (effective temperature, bolometric luminosity,…
Solar infrared colors provide powerful constraints on the stellar effective temperature scale, but to this purpose they must be measured with both accuracy and precision. We achieve this requirement by using line-depth ratios to derive in a…
We present interferometric angular sizes for 12 stars with known planetary companions, for comparison with 28 additional main-sequence stars not known to host planets. For all objects we estimate bolometric fluxes and reddenings through…
We present a new direct spectroscopic calibration for a fast estimation of the stellar metallicity [Fe/H]. These calibrations were computed using a large sample of 451 solar-type stars for which we have precise spectroscopic parameters…
Various effective temperature scales have been proposed over the years. Despite much work and the high internal precision usually achieved, systematic differences of order 100 K (or more) among various scales are still present. We present…
We derive an intrinsic colour calibration for F--K stars using broad band Johnson colours and line indices KP and HP2. Through this calibration we can determine E(B-V) of an individual star within 0.03 mag. The E(B-V) values thus derived…
External errors of effective temperatures of stars for selected libraries are estimated from data intercomparisons. It is found that the obtained errors are mainly in a good correspondence with the published data. The results may be used to…
We have investigated the relevant trend of the bolometric correction (BC) at the cool-temperature regime of red giant stars and its possible dependence on stellar metallicity. Our analysis relies on a wide sample of optical-infrared…
We derive an empirical effective temperature and bolometric luminosity calibration for G and K dwarfs, by applying our own implementation of the InfraRed Flux Method to multi-band photometry. Our study is based on 104 stars for which we…
Giant stars, and especially C-rich giants, contribute significantly to the chemical enrichment of galaxies. The determination of precise parameters for these stars is a necessary prerequisite for a proper implementation of this evolutionary…
We present further evidence that the magnetic chemically peculiar stars (CP2) of the upper main sequence already occur at very early stages of the stellar evolution, significantly before they reach 30% of their life-time on the main…
I show that the standard microlensing technique to measure the angular radius of a star using color/surface-brightness relations can be inverted, via late-time proper motion measurements, to calibrate these relations. The method is…
A novel approach to calibrate the sensitivity of a differential thermometer, consisting of several thermocouples connected in series (thermopile), has been developed. The goal of this method is to increase the accuracy of small temperature…
We analysed red giant branch stars in 16 Galactic globular clusters, computing their atmospheric parameters both from the photometry and from excitation and ionisation balances. The spectroscopic parameters are lower than the photometric…
We extend our effort to calibrate stellar isochrones in the Johnson-Cousins ($BVI_C$) and the 2MASS ($JHK_s$) filter systems based on observations of well-studied open clusters. Using cool main-sequence (MS) stars in Praesepe, we define…
We have derived the stellar atmospheric parameters, the effective temperature T$_{eff}$, the microturbulent velocity $\zeta$, the surface gravity log g, and the metallicity [Fe/H] for HE 0017+0055, HE 2144-1832, HE 2339-0837, HD 145777, and…
In a sample of six young open clusters we investigated 1753 objects using the narrow band, three filter Delta a photometric system resulting in the detection of eleven bona-fide magnetic chemically peculiar (CP) stars and five Be or…
The pre-main-sequence evolution of the chemically peculiar (CP) stars on the upper main sequence is still a vast mystery and not well understood. Our analysis of young associations and open clusters aims to find (very) young CP stars to try…
Chemically peculiar (CP) stars are unique natural laboratories for investigation of the microscopic diffusion processes of chemical elements. The element segregation under the influence of gravity and radiation pressure leads to the…
A most desirable feature of a standard candle to estimate astronomical distances is robustness against changes in metallicity and age. It is argued that the radii of main sequence stars with spectral types from solar to A0 show predictable…