Theoretical studies of the normal modes of a coronal slab often neglect gravity, as in Edwin and Roberts ( Solar Phys. 71, 239, 1982). Here we study analytically the effect of gravity acting on a horizontal slab as a first step away from a homogeneous medium. Because of the inclusion of gravity, the symmetry of a homogeneous slab is lost, so the

The neutrino production rate strongly depends on the temperature, and a small variation of chemical composition in the central regions can imply a large variation of neutrino flux. For some values of their frequencies and wavenumbers, the internal waves e xcited at the bottom of the solar convective zone are able to propagate until the central

Numerical experiments of the emergence of magnetic flux from the uppermost layers of the solar interior to the photosphere and its further eruption into the low atmosphere and corona are carried out. We use idealized models for the initial stratification and magnetic field distribution below the photosphere similar to those used for

We present high time resolution spectroscopy of the non-eclipsing old nova V533 Herculis (N Her 1963). It is the second nova remnant affected by the `SW Sex syndrome'. A modulation of the equivalent width of the emission lines with a period of 23.33 min has been detected. This, together with the strong He II λ4686 emission characteristic of

We present a study of the emission line profiles of a sample of 12 single-peaked Active Galactic Nuclei (AGNs- Sy 1 and QSOs). The narrow [OIII] lines seem to be related to two components; NLR1, which has dispersion velocities from 200 to 500 km s-1 and is blueshifted with respect to the systemic by about 20 to 350 km s-1; and NLR2, with smaller

The surface abundance of lithium on the Sun is 140 times less than the protosolar value, yet the temperature at the base of the surface convective zone is not hot enough to burn-and hence deplete-Li (refs 2, 3). A large range of Li abundances is observed in solar-type stars of the same age, mass and metallicity as the Sun, but such a range is