ﻻ يوجد ملخص باللغة العربية
We search for stellar and substellar companions of young nearby stars to investigate stellar multiplicity and formation of stellar and substellar companions. We detect common proper-motion companions of stars via multi-epoch imaging. Their companionship is finally confirmed with photometry and spectroscopy. Here we report the discovery of a new co-moving (13 sigma) stellar companion ~17.8 arcsec (350 AU in projected separation) north of the nearby star HD141272 (21 pc). With EMMI/NTT optical spectroscopy we determined the spectral type of the companion to be M3+-0.5V. The derived spectral type as well as the near infrared photometry of the companion are both fully consistent with a 0.26+-0.07 Msol dwarf located at the distance of HD141272 (21 pc). Furthermore the photometry data rules out the pre-main sequence status, since the system is consistent with the ZAMS of the Pleiades.
Period-luminosity sequences have been shown to exist among the Semi-Regular Variables (SRVs) of the Magellanic Clouds (Wood et al, 1999), the Bulge of the Milky Way galaxy (Glass & Schultheis, 2003) and elsewhere. It would clearly be useful to have a
The age-metallicity relation is a fundamental tool for constraining the chemical evolution of the Galactic disc. In this work we analyse the observational properties of this relation using binary stars that have not interacted consisting of a white d
The phase-space structure of our Galaxy holds the key to understand and reconstruct its formation. The Lambda-CDM model predicts a richly structured phase-space distribution of dark matter and (halo) stars, consisting of streams of particles torn fro
The age-metallicity relation (AMR) is a fundamental observational constraint for understanding how the Galactic disc formed and evolved chemically in time. However, there is not yet an agreement on the observational properties of the AMR for the sola
We perform a search for binary black hole mergers with one subsolar mass black hole and a primary component above $2 M_odot$ in the second observing run of LIGO/Virgo. Our analysis therefore extends previous searches into a mass region motivated by t