[en] A first approximation in the mathematical solution of the transfer equation leads to a very simple theoretical description of the stellar atmospheres. The influence of the principal parameters, temperature, pressure and chemical composition, is shown in a very clear manner

No abstract available

[en] The fraction of light blocked by metal lines in selected spectral regions is measured from coude spectra for 38 nearby A-type stars. Results are tabulated over the wavelength range 3300 A--5681 A and are useful for photometric systems employing the Oke bandpasses. Comparison with recent metal-line-blanketed stellar atmospheres is made. (auth)

[en] A series of new numerical techniques and novel uses of existing techniques are presented to solve the model stellar atmosphere problem. The techniques are applied to the fully linearized LTE problem and procedures for generalizing to the non-LTE problem are indicated. It is also shown that the usual angle quadrature schemes, particularly the n = 3 double Gauss scheme, can introduce significant errors in the calculation of the mean intensity. Alternative schemes are presented that subsequently improve on this. (author)

No abstract available

[en] This paper indicates how neutrino astronomy has begun to contribute to an understanding of the intrinsic properties of neutrinos. The author discusses Neutrino Astrophysics, concerned more with the internal constitution of stellar bodies and the intrinsic nature of their emissions than with the mechanics of the motions and the exteriors of those bodies

[en] The quasi-periodic variability of the shell star EW Lac is considered. Four-color photometry is presented which defines the time scale (approximately 0.7d) and the wavelength dependence of the variations. The observed variations are compared with those expected from several possible models for variability. The wavelength dependence of the variability is suggestive of temperature changes in an early-type atmosphere, and seems to exclude possible interpretation in terms of changing absorption, emission, or scattering in the shell. (3 figures, 1 table, 22 references) (U.S.)

[en] High-resolution observations of small-scale solar dynamics are discussed, taking into account the phase relations of high degree p-modes, power spectra of short-period oscillations, observations of high frequency waves using CCD array, dynamic signatures of quiet sun magnetic fields, and small-scale dynamical processes in the solar chromosphere. Other topics explored are related to projected improvements to high-resolution measurements, interpretation of high-resolution measurements, modelling of small-scale dynamical processes, convection and wave generation, interaction between solar convection and magnetism, low-resolution observations bearing on small-scale dynamical processes in the sun, the interpretation of low resolution observations, the accuracy of models obtained from low-resolution observations, and observations and interpretations of small-scale dynamical processes in stellar atmospheres. Attention is given to the observation of stellar granulation, and Zeeman broadening in solar type stars

[en] The base of the convection zone (CZ) is a source of acoustic glitches in the asteroseismic frequency spectra of solar-like oscillators, allowing one to precisely measure the acoustic depth to the feature. We examine the sensitivity of the depth of the CZ to mass, stellar abundances, and input physics, and in particular, the use of a measurement of the acoustic depth to the CZ as an atmosphere-independent, absolute measure of stellar metallicities. We find that for low-mass stars on the main sequence with 0.4 M_☉ ≤ M ≤ 1.6 M_☉, the acoustic depth to the base of the CZ, normalized by the acoustic depth to the center of the star, τ_cz,n, is both a strong function of mass, and varies at the 0.5%-1% per 0.1 dex level in [Z/X], and is therefore also a sensitive probe of the composition. We estimate the theoretical uncertainties in the stellar models and show that combined with reasonable observational uncertainties we can expect to measure the metallicity to within 0.15-0.3 dex for solar-like stars. We discuss the applications of this work to rotational mixing, particularly in the context of the observed mid-F star Li dip, and to distinguishing between different mixtures of heavy elements.

No abstract available