By two different methods, we show that LHS 4033 is an extremely massive white dwarf near its likely upper mass limit for destruction by unstable electron captures. From the accurate trigonometric parallax reported herein, the effective temperature (Teff=10,900 K) and the stellar radius (R=0.00368 Rsolar) are directly determined from the broadband

Old algorithms are still in use nowadays setting the Easter date accordingly to some elements giving the Spring Equinox and the New Moon for a given year. At least two different approaches (by the Orthodox and Catholic Churches) provide different results, most of the times different than the actual moments given by the two astronomical phenomena. A

Hickson compact groups (HCGs) constitute an interesting extreme in the range of environments in which galaxies are located, as the space density of galaxies in these small groups are otherwise only found in the centres of much larger clusters. The work presented here uses Lick indices to make a comparison of ages and chemical compositions of

In the modern era of helioseismology we have a wealth of high-quality data available, e.g., more than 6 years of data collected by the various instruments on board the SOHO mission, and an even more extensive ground-based set of observations covering a full solar cycle. Thanks to this effort a detailed picture of the internal rotation of the Sun

We report the results of optical monitoring of a sample of AGNs carried out in summer 2002. While rapid optical variability is a well-known aspect of blazar activity, there have been fewer studies of possible rapid variations in the spectrum, although some studies suggest that variations may exist even on scales of hours and less. Six of fourteen

We present a revised and augmented version of the Gonzalez-Perez et al. [AJ 122 (2001) 2055] catalogue of stars in quasar and blazar fields calibrated in the Landolt system. Several of the sources in this catalogue are known TeV emitters and thus of considerable interest for multifrequency campaigns. A total of 8000 measures in BVRI have been added