Related papers: Is the Young Star Association $\epsilon$Cha Double…
We present the results of radial velocity measurements of two samples of active stars. The first sample contains field G and K giants across the Red Giant Branch, whereas the second sample consists of nearby young stars (d < 150 pc) with…
The kinematic properties of young stars that have not yet reached the stage of the main sequence are studied. The selection of these stars was recently carried out by Marton et al. (2019) and Vioque et al. (2020) according to the Gaia DR2…
Surveys of young star-forming regions have discovered a growing population of planetary-mass (<13 M_Jup) companions around young stars. There is an ongoing debate as to whether these companions formed like planets (that is, from the…
It is well known that the magnetic activity of solar type stars decreases with age, but it is widely debated in the literature whether there is a smooth decline or if there is an early sharp drop until 1-2 Gyr followed by a relatively…
We derive age constraints for 1639 red giants in the APOKASC sample for which seismic parameters from Kepler, as well as effective temperatures, metallicities and [alpha/Fe] values from APOGEE DR12 are available. We investigate the relation…
Nearby associations are excellent objects for the study of the initial spin up phase during the PMS evolution. An empirical approach is adopted here to infer their rotations properties and relations to X-ray emission. Three nearby…
The stellar Rotation $vs.$ Age relation is commonly considered as a useful tool to derive reliable ages for Sun-like stars. However, in the light of \kepler\ data, the presence of apparently old and fast rotators that do not obey the usual…
We present stellar properties (mass, age, radius, distances) of 57 stars from a seismic inference using full-length data sets from Kepler. These stars comprise active stars, planet-hosts, solar-analogs, and binary systems. We validate the…
We present the results of a multiplicity survey of 126 stars spanning ~0.1-3 solar masses in the ~2-Myr-old Chamaeleon I star-forming region, based on adaptive optics imaging with the ESO Very Large Telescope. Our observations have revealed…
The Serpens OB2 association (l ~ 18.5 deg, b ~ 1.9 deg, d = 1950 +/- 30 pc) is a large star-forming complex ~65 pc above the Galactic midplane, with a clumpy, elongated structure extending ~50 pc parallel to the plane. We analyse probable…
From correlations between orbital parameters, several new coherent groups of stars were recently identified in the Galactic disc and suggested to correspond to remnants of disrupted satellites. To reconstruct their origin at least three…
An asteroid pair can be described as two asteroids with highly similar heliocentric orbits that are genetically related but not gravitationally bound. They can be produced by asteroid collisions or rotational fission. Although over 200…
We have used precise radial velocity measurements for a large number of candidate low-mass stars and brown dwarfs, to show that the young Sigma Ori ``cluster'' consists of two spatially superimposed components which are kinematically…
The kinematics of low-mass stars in nearby OB associations can provide clues about their origins and evolution. Combining the precise positions, proper motions and parallaxes given in the second Gaia Data Release with radial velocity…
A significant population of stars with ages younger than the Pleiades exists in the solar neighborhood. They are grouped in loose young associations, sharing similar kinematical and physical properties, but, due to their vicinity to the…
We have reanalyzed data for the proposed moving group associated with beta Pic in order to determine if the group (or part of it) is real, and, if so, to derive an improved age estimate for beta Pic. By using new, more accurate proper…
The kinematic properties of the Sco-Cen association have been studied using the spatial velocities of young stars. New kinematic age estimates for the three components of the association with the age of UCL and LCC being $17.7\pm2.4$ Myrs…
The advent of Gaia has led to the discovery of nearly 300 elongated stellar associations (called `strings') spanning hundreds of parsecs in length and mere tens of parsecs in width. These newfound populations present an excellent laboratory…
This article reviews some recent studies of the mass, age, and space distributions of star clusters, with a primary focus on the large population of clusters in the interacting Antennae galaxies. Some of the highlights of these studies are…
Stars form predominantly in groups which display a broad spectrum of masses, sizes, and other properties. Despite this diversity there exist an underlying structure that can constrain cluster formation theories. We show how combining…