The gaseous component of the reflection nebula surrounding HD 26676 is investigated by comparing the UV spectrum of the star with that of the foreground star HD 26793. The physical properties of the cloud are constrained under the assumption of Mg photoionization and H ionization by cosmic rays and taking into account the effect of the stellar

Measurements of lithium in stars of different galactic populations such as young open clusters (Alpa Per, Pleiades, Praesepe, Coma, Hyades), very young stellar associations (Taurus-Auriga, Chamaeleon, Ophiuchus clouds), intermediate and old open clusters (NGC 752, M 67, NGC 188), old disk stars, and halo stars give the observational framework from

A two-dimensional velocity map in H-alpha of the inner 4 arc min zone of the Scd starburst galaxy NGC 6946 has been obtained using the TAURUS interferometric spectrometer on the 2.5 m Isaac Newton Telescope. The major axis rotation curve is a clean kinematic superposition of a central 1 kpc sphere with solid body rotation and a disk with density

For determining the adiabatic stability of a uniform vertical field in an arbitrary stratification it is sufficient to consider the limit of infinitesimal horizontal wavelength. It is shown how the behavior of the instability can be estimated qualitatively from the dependence of the equipartition field strength on depth. Modes are calculated

We report the first results obtained from a continuing programme of spectrophotometric monitoring of high luminosity active galactic nuclei (AGN). Analysis shows that significant emission line variations take place in high luminosity, high redshift objects. These variations occur on time-scales much shorter than those expected from photo-ionization

The 2.5-m Isaac Newton telescope has been used in a spectrophotometric monitoring program of high-luminosity AGN. The data acquisition and analysis techniques are first discussed. A comparison of the L-alpha, C IV, and C III profiles reveals that the profiles of different lines in a single object are not always the same as each other. An analysis