Related papers: How accurately can we age-date solar-type dwarfs u…
Sun-like stars are well represented in the solar neighbourhood but are currently under-utilised, with many studies of chemical and kinematic evolution focusing on red giants (which can be observed further away) or turn-off stars (which have…
Stellar activity and rotation frustrate the detection of exoplanets through the radial velocity technique. This effect is particularly of concern for M dwarfs, which can remain magnetically active for billions of years. We compile rotation…
There is now a large sample of stars observed by the Kepler satellite with measured rotation periods and photometric activity index $S_{\rm ph}$. We use this data, in conjunction with stellar interiors models, to explore the interplay of…
Chromospheric activity has been thought to decay smoothly with time and, hence, to be a viable age indicator. Measurements in solar type stars in open clusters seem to point to a different conclusion: chromospheric activity undergoes a fast…
Gyrochronology and recent theoretical findings are used to reduce the number of input parameters of differential rotation models. This eventually leads to a theoretical prediction for the surface differential rotation as a function of only…
We have constructed a catalog containing best available astrometric, photometric, radial velocity and astrophysical data for mainly F-type and G-type stars (called the Astrometric catalog associated with Astrophysical Data, ACAD), which…
The surface rotation rates of young solar-type stars decrease rapidly with age from the end of the pre-main sequence though the early main sequence. This suggests that there is also an important change in the dynamos operating in these…
Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by H-alpha emission), rotation period, and…
Age is a stellar parameter that is both fundamental and difficult to determine. Among middle-aged M dwarfs, the most prolific hosts of close-in and detectable exoplanets, gyrochronology is the most promising method to assign ages, but…
Recent observations reveal the surprising breakdown of stellar gyrochronology relations at about the Sun's age hinting that middle-aged, solar-like stars transition to a magnetically inactive future. We provide a theoretical basis for these…
Rotation is a directly-observable stellar property, and drives magnetic field generation and activity through a magnetic dynamo. Main sequence stars with masses below approximately 0.35Msun (mid-to-late M dwarfs) are fully-convective, and…
The ages of the most common stars - low-mass (cool) stars like the Sun, and smaller - are difficult to derive because traditional dating methods use stellar properties that either change little as the stars age or are hard to measure. The…
We investigate the relationship between age and chromospheric activity for 139 M dwarf stars in wide binary systems with white dwarf companions. The age of each system is determined from the cooling age of its white dwarf component. The…
Multi-wavelength studies of solar analogs (G0-5 V stars) with ages from ~50 Myr to 9 Gyr have been carried out as part of the "Sun in Time" program for nearly 20 yrs. From these studies it is inferred that the young (ZAMS) Sun was rotating…
We have examined the relationship between rotation and activity in 14 late-type (M6-M7) M dwarfs, using high resolution spectra taken at the W.M. Keck Observatory and flux-calibrated spectra from the Sloan Digital Sky Survey. Most were…
By using the current photometric rotational data on eight galactic open clusters, we show that the evolutionary stellar model (isochrone) ages of these clusters are tightly correlated with the period shifts applied to the (B-V)_0 - P_rot…
We present a study of the dynamics and magnetic activity of M dwarfs using the largest spectroscopic sample of low-mass stars ever assembled. The age at which strong surface magnetic activity (as traced by H-alpha) ceases in M dwarfs has…
Solar simulations and observations show that the detection of long-period Earth-like planets is expected to be very difficult with radial velocity techniques in the solar case because of activity. The inhibition of the convective blueshift…
Gyrochronology, the field of age-dating stars using mainly their rotation periods and masses, is ideal for inferring the ages of individual main-sequence stars. However, due to the lack of physical understanding of the complex magnetic…
The ages of young star clusters are fundamental clocks to constrain the formation and evolution of pre-main-sequence stars and their protoplanetary disks and exoplanets. However, dating methods for very young clusters often disagree,…