Related papers: Coronal activity among open cluster stars

As the closest open cluster to the Sun, the Hyades is an important benchmark for many stellar properties, but its members are also scattered widely over the sky. Previous studies of stellar rotation in the Hyades relied on targeted…

We present a sample of 14 M dwarf stars observed with XMM-Newton and Chandra, for which we also computed rotational periods from Kepler Two-Wheel (K2) Mission light curves. We compiled X-ray and rotation data from the literature and…

The rotation periods of the host stars of extrasolar planets have been assessed against those of the Mt. Wilson stars, open cluster stars, and evolutionary stellar models that include rotation. They appear to be normal, modulo certain…

Stars spend most of their lifetimes on the `main sequence' (MS) in the Hertzsprung--Russell diagram. The obvious double MSs seen in the equivalent color--magnitude diagrams characteristic of Milky Way open clusters pose a fundamental…

Luminous X-ray stars are very often found in visual double or multiple stars. Binaries with periods of a few days possess the highest degree of coronal X-ray activity among regular, non-relativistic stars because of their fast, tidally…

(Abridged) Understanding stellar activity in M dwarfs is crucial for the physics of stellar atmospheres as well as for ongoing radial velocity exoplanet programmes. Despite the increasing interest in M dwarfs, our knowledge of the…

The present state of X-ray observations of cool stars in coeval open clusters is reviewed. Concentrating on ROSAT results for solar-type stars, the available observational dataset is summarized along with those details of the evolution of…

We present the results of a photometric survey of rotation rates in the Coma Berenices (Melotte 111) open cluster, using data obtained as part of the SuperWASP exoplanetary transit-search programme. The goal of the Coma survey was to…

Our goal is to determine the rotational and magnetic-related activity properties of stars at different stages of evolution. We have focussed our attention on 6 young loose stellar associations within 100 pc and ages in the range 8-70 Myr:…

Stellar activity influences radial velocity (RV) measurements and can also mimic the presence of orbiting planets. As part of the search for planets around the components of wide binaries performed with the SARG High Resolution Spectrograph…

Which sample of objects can give strong constraints on single-star evolution theory ? Whilst star cluster members share the same age and the same metallicity, many questions (e.g. field stars contamination, stellar rotation, presence of…

We review the current state of our knowledge concerning the rotation and angular momentum evolution of young stellar objects and brown dwarfs from a primarily observational view point. Periods are typically accurate to 1% and available for…

We have obtained high-resolution echelle spectra of 18 solar-type stars that an earlier survey showed to have very high levels of Ca II H and K emission. Most of these stars belong to close binary systems, but 5 remain as probable single…

Stellar activity cycles reveal continuous relaxation and induction of magnetic fields. The activity cycle is typically traced through the observation of cyclic variations in total brightness or Ca H&K emission flux of stars, as well as…

Using the results of our first paper on the Chandra HRC observation of the Orion Nebula Cluster (ONC), here we explore the relation between the coronal activity of its 1-Myr-old pre-main sequence population and stellar parameters. We find…

We probed stellar X-ray activity over a wide range of stellar parameters, using {\it Chandra} and LAMOST data. We measured the X-ray-to-bolometric luminosity ratio ($R_X = L_X/L_{\rm bol}$) for 484 main-sequence stars, and found a bimodal…

The Praesepe open cluster represents a puzzle since it has about the same age as the Hyades, and only slightly different metallicity, yet previous ROSAT observations resulted in a detection rate of cluster sources significantly lower than…

At fast rotation rates the coronal activity of G- and K-type stars has been observed to "saturate" and then decline again at even faster rotation rates -- a phenomenon dubbed "super-saturation". In this paper we investigate coronal activity…

We have assembled a sample of $\sim$8200 stars with spectral types F5V-M5V, all having directly measured X-ray luminosities from eROSITA and rotation periods from TESS, and having empirically estimated ages via their membership in stellar…

We discuss oxygen abundances derived from [O I] 6300 and the O I triplet in stars spanning a wide range in chromospheric activity level, and show that these two indicators yield increasingly discrepant results with higher…