Related papers: F stars: A challenge to stellar evolution
We calculated the broad-band photometric evolution of unresolved star clusters, including the preferential loss of low-mass stars due to mass segregation. The stellar mass function of a cluster evolves due to three effects: (a) the…
The thermal evolution of strange stars in both normal and color-flavor-locked (CFL) phases are investigated together with the evolutions of the stellar rotation and the r-mode instability. The heating effects due to the deconfinement…
Calcium abundance in the atmosphere of Am stars is examined as a function of their evolutionary state within the main sequence. New spectroscopic abundances as well as abundances abtained photometrically by Guthrie (1987) are used, since…
The ultraviolet (UV) emission from the most numerous stars in the universe, M dwarfs, impacts the formation, chemistry, atmospheric stability, and surface habitability of their planets. We have analyzed the spectral evolution of UV emission…
Stellar evolution theory is most uncertain for massive stars. For reliable predictions of the evolution of massive stars and their final fate, solid constraints on the physical parameters, and their changes along the evolution and in…
Active region evolution plays an important role in the generation and variability of magnetic fields on the surface of lower main-sequence stars. However, determining the lifetime of active region growth and decay as well as their evolution…
Globular star clusters that formed at the same cosmic time may have evolved rather differently from a dynamical point of view (because that evolution depends on the internal environment) through a variety of processes that tend…
For many decades the determination of accurate fundamental parameters for stars (masses, radii, temperatures, luminosities, etc.) has mostly been the domain of eclipsing binary systems. That has begun to change as long-baseline…
We present the first results on the saturation of the f-mode instability in neutron stars, due to nonlinear mode coupling. Emission of gravitational waves drives the f-mode (fundamental mode) unstable in fast-rotating, newborn neutron…
The form of the early-type galaxy scaling relation (the Fundamental Plane or FP) is a direct indicator of the underlying physical origins for the galaxy sequence. Observed properties of the FP include: (1) the slope increases with…
Observing the stars in our night sky tells us that giant, supergiant and hypergiant stars hold an unique importance in the understanding of stellar populations. Theoretical stellar models predict a rich tapestry of evolved stars. These…
Excess chromospheric emissions within deep photospheric lines are effective proxies of stellar magnetism for FGK stars. This emission decays with stellar age and is a potential determinant of this important stellar quantity. We report…
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 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…
A knowledge of stellar ages is crucial for our understanding of many astrophysical phenomena, and yet ages can be difficult to determine. As they become older, stars lose mass and angular momentum, resulting in an observed slowdown in…
The dependences of the velocity ellipsoids of F-G stars of the thin disk of the Galaxy on their ages and metallicities are analyzed based on the new version of the Geneva-Copenhagen Catalog. The age dependences of the major, middle, and…
The measurement of stellar properties such as chemical compositions, masses and ages, through stellar spectra, is a fundamental problem in astrophysics. Progress in the understanding, calculation and measurement of atomic properties and…
Stars in globular clusters (GCs) exhibit a peculiar chemical pattern with strong abundance variations in light elements along with a constant abundance in heavy elements. These abundance anomalies can be explained by a primordial pollution…
When determining absolute ages of identifiably young stellar populations, results strongly depend on which stars are studied. Cooler (K, M) stars typically yield ages that are systematically younger than warmer (A, F, G) stars by a factor…
Although photometric and spectroscopic surveys with the Spitzer Space Telescope increased remarkably the number of well studied debris disks around A-type and Sun-like stars, detailed analyzes of debris disks around F-type stars remained…