Related papers: Rotational evolution of very low mass objects and …
For a rotating galaxy, the inner circular-velocity gradient d_{R}V(0) provides a direct estimate of the central dynamical mass density, including gas, stars, and dark matter. We consider 60 low-mass galaxies with high-quality HI and/or…
Observational and theoretical investigations provide evidence for non-uniform spot and magnetic flux distributions on rapidly rotating stars, which have a significant impact on their angular momentum loss rate through magnetised winds.…
At metallicities lower than that of the Small Magellanic Cloud, it remains essentially unexplored how fossil magnetic fields, forming large-scale magnetospheres, could affect the evolution of massive stars, thereby impacting the fundamental…
A sample of 97 galactic field Be stars were studied by taking into account the effects induced by the fast rotation on their fundamental parameters. All program stars were observed in the BCD spectrophotometric system in order to minimize…
Stellar rotation is a crucial parameter driving stellar magnetism, activity and mixing of chemical elements. Furthermore, the evolution of stellar rotation is coupled to the evolution of circumstellar disks. Disk-braking mechanisms are…
Employing realistic and consistent atmosphere boundary conditions, we have generated evolutionary models for brown dwarfs and very-low-mass stars (VLMs) for different metallicities ([Fe/H]), with and without clouds. We find that the spread…
We surveyed thirteen very low mass (VLM; M < 0.2 M_sun) objects in the Taurus star-forming region using near-infrared diffraction-limited imaging techniques on the W.M. Keck I 10 m telescope. Of these thirteen, five were found to be binary,…
We present a brief review of observational results contributing to modern ideas on the evolution of stellar activity. Basic laws, derived for both rotation-age and activity-rotation relationships, allow us to trace how the activity of…
The evolution of star clusters is determined by several internal and external processes. Here we focus on two dominant internal effects, namely energy exchange between stars through close encounters (two-body relaxation) and mass-loss of…
Close M-dwarf binaries and higher multiples allow the investigation of rotational evolution and mean magnetic flux unbiased from scatter in inclination angle and age since the orientation of the spin axis of the components is most likely…
We examine how the fraction $f$ of stars for which rotational modulation has been detected in Kepler light curves depends on the stellar mass $M_\star$ and age $t_\star$. Our sample consists of $\approx 850$ FGK stars hosting transiting…
Planets orbiting young, solar-type stars are embedded in a more energetic environment than that of the solar neighbourhood. They experience harsher conditions due to enhanced stellar magnetic activity and wind shaping the secular evolution…
The evolution of magnetic fields in Ap stars during the main sequence phase is presently mostly unconstrained by observation because of the difficulty of assigning accurate ages to known field Ap stars. We are carrying out a large survey of…
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…
Stellar rotation is a strong function of both mass and evolutionary state. Missions such as Kepler and CoRoT provide tens of thousands of rotation periods, drawn from stellar populations that contain objects at a range of masses, ages, and…
We develop new angular momentum evolution models for stars with masses of $0.5$ to $1.6~\rm M_\odot$ and from the pre-main-sequence (\rm PMS) through the end of their main-sequence (\rm MS) lifetime. The parametric models include magnetic…
The rotational evolution of cool dwarfs is poorly constrained after around 1-2 Gyr due to a lack of precise ages and rotation periods for old main-sequence stars. In this work we use velocity dispersion as an age proxy to reveal the…
Rotation may affect the occurrence of sustainable hydrogen burning in very low-mass stellar objects by the introduction of centrifugal force to the hydrostatic balance as well as by the appearance of rotational break-up of the objects…
Rotation is one of the key stellar parameters which undergo substantial evolution during the stellar lifetime, in particular during the early stages. Stellar rotational periods can be determined on the basis of the periodic modulation of…
The Be star sample of Steele et al. (1998) has a distribution of v sin i's that is luminosity dependant, with giants having lower projected rotational velocities than dwarfs. We show that this effect can be understood simply in terms of…