The Delta Scuti variable 63 Her was observed during 21 nights at two observatories (Observatorio del Teide, Tenerife Island, Spain and Observatorio Astronomico Nacional de San Pedro Martir in Baja California, Mexico). Six frequencies of pulsation are unambiguously detected, among which the fundamental radial mode, two non radial pressure-like modes

A method to obtain the Duvall phase function from the structure of a stellar model is presented. This can be a good tool for understanding the dependence of p-mode frequencies on the structure of the upper layers of the convection zone. A linear relation between phase function differences of two models and their equilibrium structure differences is

The suitability of the Eddington approximation as a theoretical framework for the study of the possibility of a k-like overstability mechanism as the driving force of solar modes of oscillation is assessed. A theoretical description of the interaction between the hydrodynamics of the motion and the radiative energy transport is needed. It is found

The small imaging photometer of the VIRGO (Variability in IRradiance and Gravity Oscillations) investigation on ESA's SOHO mission is presented. This instrument, the Luminosity Oscillations Imager (LOI), will observe the solar radiance with 12 pixels resolution. A prototype of the LOI was built mainly to test possible detector configurations, the

The iron abundance of seven stars near the main-sequence (MS) turnoff and a giant in M67 are spectroscopically derived, and the results are discussed. The resulting mean iron abundance of the turnoff stars is (Fe/H) = 0.04 + or - 0.04. Taken together with previous determinations for younger clusters, this shows that there has been relatively little

Estimates of the spectral linewidths of low degree (Q=0 and Q=1) 5 min p-modes obtained from Doppler shift observations in 1984, 1986, and 1987 are reported. The observed linewidths increase from 0.5 microHz at 2000 microHz to 3.8 microHz at 4300 microHz for Q = 0. Comparison with other data suggests that for a given frequency the linewidth