Related papers: Estimating the Convective Turnover Time
We analyse the relation between the activity cycle length and the Rossby number and collected a sample of 44 main sequence stars with well-known activity cycle periods and rotation periods. We find a linear behaviour in the…
We present a Monte Carlo analysis of the recently introduced variability indices $\tau$ (Tompkins 1999) and $I$ (Zhang et al. 2000 & Torres et al. 2001) for $\gamma$-ray sources. We explore different variability criteria and prove that…
Several observational studies have shown that many Galactic globular clusters (GCs) are characterised by internal rotation. Theoretical studies of the dynamical evolution of rotating clusters have predicted that, during their long-term…
Turbulent motions in the interior of a star play an important role in its evolution, since they transport chemical species, thermal energy and angular momentum. Our overall goal is to construct a practical turbulent closure model for…
Stellar surface rotation carries information about stellar parameters---particularly ages---and thus the large rotational datasets extracted from Kepler timeseries represent powerful probes of stellar populations. In this article, we…
Using a sample of Nova-like stars from the Ritter and Kolb catalog, we examine the relationship between their Gaia determined absolute magnitude and the inclination of the binary system. Webbink et al. (1987) derived a relationship between…
The intermediate period gap, discovered by Kepler, is an observed dearth of stellar rotation periods in the temperature-period diagram at $\sim$ 20 days for G dwarfs and up to $\sim$ 30 days for early-M dwarfs. However, because Kepler…
We analyse 829,481 stars from the Next Generation Transit Survey (NGTS) to extract variability periods. We utilise a generalisation of the autocorrelation function (the G-ACF), which applies to irregularly sampled time series data. We…
Stellar mass is a fundamental parameter that is key to our understanding of stellar formation and evolution, as well as the characterization of nearby exoplanet companions. Historically, stellar masses have been derived from long-term…
To reveal the detail of the internal structure, the relationship between chromospheric activity and the Rossby number, N_R (= rotational period P / convective turnover time tau_c), has been extensively examined for main-sequence stars. The…
Understanding how the magnetic activity of low-mass stars depends on their fundamental parameters is an important goal of stellar astrophysics. Previous studies show that activity levels are largely determined by the stellar Rossby number…
We investigate the rotational evolution of solar-like stars with a focus on the internal angular momentum transport processes. The double zone model, in which the star's radiative core and convective envelope are assumed to rotate as solid…
Long-term stellar activity variations can affect the detectability of long-period and Earth-analogue extrasolar planets. We have, for 54 stars, analysed the long-term trend of five activity indicators: log$R'_\mathrm{{HK}}$, the…
Introduction The tau statistic is a recent second-order correlation function that can assess the magnitude and range of global spatiotemporal clustering from epidemiological data containing geolocations of individual cases and, usually,…
The presence of a massive close-in planet with an orbital period of a few days or less around a low-mass star can possibly results in a strong variation of the properties of the central star. Indeed, star-planet tidal interactions generate…
The two most common techniques for measuring planetary masses - the radial velocity (RV) and the transit timing variations (TTVs) techniques - have been observed to yield systematically different masses for planets of similar radii.…
Over the past 40 years, observational surveys have established the existence of a tight relationship between a star's age, rotation period, and magnetic activity. This age-rotation-activity relation documents the interplay between a star's…
We report on 13 new high-precision measurements of stellar diameters for low-mass dwarfs obtained by means of near-infrared long-baseline interferometry with PIONIER at the Very Large Telescope Interferometer. Together with accurate…
We use observational data on the magnitude-redshift relation for Type Ia supernovae together with constraints on the ages of the oldest stars to rule out a higher-dimensional extension of General Relativity with a negative kinetic-energy…
Using the most recent results about white dwarfs in 10 open clusters, we revisit semi-empirical estimates of the initial-final mass relation in star clusters, with emphasis on the use of stellar evolution models. We discuss the influence of…