A project to search for nearby stars in a wide field using Schmidt plates is presented. A field intensively observed allowed us to select a list of nearby stars candidates. CCD astrometry of 20 of these, acquired at the 1.23m telescope of Calar Alto is presented. Trigonometric parallaxes and proper motions have been determined. We confirm for six of our targets that they are nearby stars with d...

Aims. We aim to measure very precise and accurate model-independent masses distances of detached binary stars. Precise at the < 1% level are necessary test calibrate stellar interior evolution models, while independent orbital parallaxes essential check for next Gaia data releases. Methods. combined RV measurements with interferometric observations determine physical parameters ten double-li...

We analyze the K band luminosities of a sample of galactic long-period variables using parallaxes measured by the Hipparcos mission. The parallaxes are in most cases re-computed from the Hipparcos Intermediate Astrometric Data using improved astrometric fits and chromaticity corrections. The K band magnitudes are taken from the literature and from measurements by COBE, and are corrected for int...

We have used the Hipparcos parallaxes to study the evolutionary status of a sample of stars with spectral types from late F to M0 (hereafter “solar-type stars”), selected on the basis of their activity, mainly from Einstein-based surveys. The parallaxes have been used to place the objects in the H-R diagram, determining their age by comparison with theoretical evolutionary tracks and observatio...

CONTEXT. Gaia EDR3 has produced parallaxes for 1.468x10^9 sources but there are calibration issues that require corrections to the published values and uncertainties. AIMS. We want characterize behavior of uncertainties parallaxes. also aim provide a procedure calculation distances stars stellar clusters. METHODS. reanalyze some data in papers QSO LMC combine those results with measurements six...