相关论文: Driving in ZZ Ceti stars - Problem solved?
As part of an ongoing program to map better the empirical instability strip of pulsating ZZ Ceti white dwarfs, we present a brief progress report based on our last observing season. We discuss here high-speed photometric measurements for 6…
Space missions have produced an incredibly large database on pulsating stars. The light curves via the frequency content contain a detailed description of each star. The critical point is the identification of modes, especially in the…
Context. The relative importance of AC and DC heating in maintaining the temperature of the corona is not well constrained. Aims. Investigate the effects of the characteristic time scales of photospheric driving on the injection and…
We report the discovery of the first identified pulsating DA white dwarf in the field of the Kepler mission, WD J1916+3938 (Kepler ID 4552982). This ZZ Ceti star was first identified through ground-based, time-series photometry, and…
The time-dependence of heating in solar active regions can be studied by analyzing the slope of the emission measure distribution cool-ward of the peak. In a previous study we showed that low-frequency heating can account for 0% to 77% of…
The effect of rotation on the cooling of neutron stars is investigated. The thermal evolution equations are solved in two dimensions with full account of general relativistic effects. It is found that rotation is particularly important in…
Massive B type pulsators such as beta Cep and slowly pulsating B (SPB) stars pulsate due to layers of increased opacity caused by partial ionization. The increased opacity blocks the energy flux to the surface of the stars which causes the…
Conduction may play an important role in reducing cooling flows in galaxy clusters. We analyse a sample of sixteen objects using Chandra data and find that a balance between conduction and cooling can exist in the hotter clusters (T > 5…
Thermal conduction in tangled magnetic fields is reduced because heat conducting electrons must travel along the field lines longer distances between hot and cold regions of space than if there were no fields. We consider the case when the…
Heat conduction plays an important role in the balance between heating and cooling in many astrophysical objects, e.g. cooling flows in clusters of galaxies. Here we investigate the effect of heat conduction on the interaction between a…
Lithium is an excellent tracer of mixing in stars as it is destroyed (by nuclear reactions) at a temperature around $\sim 2.5\times 10^6$ K. The lithium destruction zone is typically located in the radiative region of a star. If the…
We estimate the thermal conductivity of a weakly collisional magnetized plasma with chaotic magnetic field fluctuations. When the fluctuation spectrum extends over two or more decades in wave-vector, we find that thermal conduction is very…
We report the discovery of two new ZZ Ceti pulsators, LP 133-144 and HE 1258+0123, selected on the basis of model atmosphere fits to optical spectroscopic data. The atmospheric parameters for LP 133-144, Teff = 11,800 +/- 200 K and log g =…
Ultra-massive DA WD stars are expected to harbor ONe cores resulting from the progenitor evolution through the Super-AGB phase. As evolution proceeds during the WD cooling phase, a crystallization process resulting from Coulomb interactions…
Recent observations have found several candidates for old warm neutron stars whose surface temperatures are above the prediction of the standard neutron star cooling scenario, and thus require some heating mechanism. Motivated by these…
For the first time connection between the pulsation and modulation properties of RR Lyrae stars has been detected. Based on the available data it is found that the possible range of the modulation frequencies, i.e, the possible maximum…
Using linear non-adabatic pulsation analysis, we explore the radial-mode (p-mode) stability of stars across a wide range of mass (0.2 <= M <= 50 Msun), composition (0 <= X <= 0.7, Z=0.001, 0.02), effective temperature (3 000 <= T_eff <= 40…
We have explored the possibility of driving pulsation modes in models of sdO stars in which the effects of element diffusion, gravitational settling and radiative levitation have been neglected so that the distribution of iron-peak elements…
Planetary systems are angular momentum reservoirs generated during star formation. This accretion process produces very powerful engines able to drive the optical jets and the molecular outflows. A fraction of the engine energy is released…
Employing a cranking Hamiltonian, in the static path approximation to the partition function, we have studied the behaviour of the moment of inertia of $^{64}Zn$ at a few values of temperatures as a function of the rotation frequency. At a…