Supernova 1991F appeared in the lenticular galaxy NGC 3458 (UGC 6037). On discovery, it was classified as type I, although no subtype (i.e., Ia or Ib/c) was assigned to it. In this paper, we present several low resolution spectra of this supernova. One of them was recorded ten days after the discovery. Two others show the supernova spectral

HD 36705 (AB Doradus) and HD 155555 (V824 Ara) are two nearby very active cool stars. Both have strong Li I (lambda)6708 resonance lines, implying high surface Li abundances, comparable to those of very young T Tauri stars. They also have late M-type visual companions which share their proper motion, as confirmed by new astrometric measurements

We show that the solution of the radiative transfer equation (RTE) through a line of sight that pierces several times two alternate atmospheres can be obtained in terms of the solutions of the RTE through both single atmospheres separately considered. This also applies to the response functions of the observed Stokes spectrum to perturbations of

Motivated by the problems of magnetic flux storage and dynamo action in stars with convection zones, we study the equilibrium and stability of magnetic flux tubes under the influence of differential rotation and stratification. The formalism developed in the first paper in this series is applied to axisymmetric, toroidal flux tubes (flux rings)

The Luminosity Oscillations Imager is a part of the VIRGO instrument to be flown aboard the Solar and Heliospheric Observatory in mid 1995. Using a ground-based version of the instrument, we have detected low-l modes with a time series spanning 163 days. The low resolution capability of the instrument allows the identification of individual

Spectroscopy of Hen 401 (IRAS 10178-5958) and WRA 751 (IRAS 11065-6026) reveal strong HI, HeI, FeII and forbidden emission lines. Images of Hen 401 reveal the bipolar morphology of the nebula.