We present the first light curves in the infrared j and K filters, obtained in different runs during 1990, 1991, and 1994. The solutions of these IR light curves together with the previous determinations, gathered from visual light curves and spectroscopic studies, finally yield stellar parameters that can be accepted with confidence. The study of

Optical spectroscopy of the highly collimated bipolar nebulae He 2-25, Th 2-B and 19W32 is presented. He 2-25 and Th 2-B are found to have very dense (N_e~10^7 cm^-3) cores characterized by emission lines of low- to intermediate-ionization species, including rich [FeII] emission. The Hα profiles present broad non-Gaussian wings. These spectral

LZ Cen is a double-lined, near-contact but detached eclipsing binary consisting of two evolved early B stars (B0.5-B1). This paper presents the first photoelectric and spectroscopic analysis of the system, based on new light curves and spectroscopic data. uvby light curves were obtained with the Danish 50 cm telescope at ESO, La Silla (916 points

In this paper we discuss the observational consequences of a dependence of meteor brightness on the entry angle z_R_, namely the decrease of the observed rates of meteors and the reduction of the population indices r for radiant zenith distances larger than zero. These effects, if not properly accounted for, lead to erroneous values of meteor

BROWN dwarfs are cool star-like objects that have insufficient mass to maintain stable nuclear fusion in their interiors. Although brown dwarfs are not stars, they are expected to form in the same way, and their frequency of occurrence should reflect the trends seen in the birthrates of low-mass stars. But finding brown dwarfs has proved to be

CLUSTERS of galaxies are the largest gravitationally bound systems in the Universe and therefore provide important constraints on the formation and evolution of large-scale structure. Cluster evolution can be inferred from observations of the X-ray emission of the gas in distant clusters, but interpreting these data is not straightforward. In a