Related papers: Rotation, activity, and lithium abundance in cool …
I review basic observational features in Population I stars which strongly implicate rotation as a mixing agent; these include dispersion at fixed temperature in coeval populations and main sequence lithium depletion for a range of masses…
An important aspect in the evolutionary scenario of cool stars is their rotation and the rotationally induced magnetic activity and interior mixing. Stars in open clusters are particularly useful tracers for these aspects because of their…
The discovery of the Spite plateau in the abundances of 7Li for metal-poor stars led to the determination of an observationally deduced primordial lithium abundance. However, after the success of the Wilkinson Microwave Anisotropy Probe…
Stellar clusters are open windows to understand stellar evolution. Specifically, the change with time and the dependence on mass of different stellar properties. As such, they are our laboratories where different theories can be tested. We…
In radiative layers of rotating stars the luminosity carried by circulation currents through a surface of constant entropy (circulation luminosity) is shown to be positive. The corresponding decrease in the temperature gradient is important…
Brightness variations due to dark spots on the stellar surface encode information about stellar surface rotation and magnetic activity. In this work, we analyze the Kepler long-cadence data of 26,521 main-sequence stars of spectral types M…
By using the LAMOST time-domain survey data, we study stellar activities based on the $\rm{H_{\alpha}}$ lines for about 2000 stars in four $K$2 plates. Two indices, $R_{\rm{H\alpha}}^{'}$ and $R_{\rm{H\alpha}}^{+}$, are computed from LAMOST…
Lithium is a sensitive probe to mixing processes operating in stellar interiors. For many years, a connection has been suspected to exist between lithium abundances and stellar rotation, presumably the result of rotationally-induced…
In this work we present the results of our analysis of 16,300 medium-resolution LAMOST spectra of late-type stars in the Kepler field with the aim of determining the stellar parameters, activity level, lithium atmospheric content, and…
There is evidence in the 125-Myr Pleiades cluster, and more recently in the 5-Myr NGC 2264 cluster, that rotation plays a key role in the Lithium (Li) depletion processes among low-mass stars. Fast rotators appear to be less Li-depleted…
We report on a study of 36 pairs of `twin' M dwarfs in wide binaries and assess how similarly the stars behave. Stars in each twin pair have BP, RP, $J$, $H$, and $K_s$ differing by $<$0.10 mag, mass estimates matching within $<$3%, and…
We investigate magnetic activity properties of 21 stars via medium resolution optical spectra and long-term photometry. Applying synthetic spectrum fitting method, we find that all targets are cool giant or sub-giant stars possessing…
We compare the Li abundances of a sample of stars with planets discovered with the Doppler method to a sample of stars without detected planets. We prepared the samples by combining the Li abundances reported in several recent studies in a…
The surface content of lithium (Li) and beryllium (Be) in stars can reveal important information about the temperature structure and physical processes in their interior regions. This study focuses on solar-type stars with a sample that is…
We present rotation periods for thousands of active stars in the Kepler field derived from Q3 data. In most cases a second period close to the rotation period was detected, which we interpreted as surface differential rotation (DR). Active…
The objective of this work is to determine what fraction of red-giant (RG) stars shows photometric rotational modulation, and understand its origin. One of the underlying questions is the role of close binarity in this population, standing…
We report results from lithium abundance determinations using high resolution spectral analysis of the 107 metal-rich stars from the Calan-Hertfordshire Extrasolar Planet Search programme. We set out to understand the lithium distribution…
This work presents a homogeneous determination of lithium abundances in a large sample of giant-planet hosting stars (N=117), and a control sample of disk stars without detected planets (N=145). The lithium abundances were derived using a…
Stars similar to the Sun, known as solar analogues, provide an excellent opportunity to study the preceding and following evolutionary phases of our host star. The unprecedented quality of photometric data collected by the \Kepler NASA…
We have determined precise stellar parameters and lithium abundances in a sample of 117 stars with basic properties very similar to the Sun. This sample selection reduces biasing effects and systematic errors in the analysis. We estimate…