The origin of the abundance discrepancy, i.e., the fact that abundances derived from recombination lines are larger than those from collisionally excited lines, is one of the key problems in the physics of photoionized nebulae. In this work, we analyze and discuss data for a sample of Galactic and extragalactic H II regions where this abundance

Fulleranes, the hydrogenated fullerenes C60H36 and C60D36 have been synthesized in n-hexane where they show an absorption maximum at 217 nm in their electronic absorption spectra with molar extinction coefficients ɛ217 = 17140 and 16480L cm-1 mol-1, respectively, which correspond to absorption cross-sections of order 6500 Mbarn, about 10 times

We present a study of short-period, central helium-burning variable stars in the Local Group dwarf spheroidal galaxy LeoI, including 106 RR Lyrae stars and 51 Cepheids. So far, this is the largest sample of Cepheids and the largest Cepheids to RR Lyrae ratio found in such a kind of galaxy. Comparison with other Local Group dwarf spheroidals, Carina

Observations of aurorae borealis at low latitudes are very rare and are clearly associated with strong geomagnetic storms. Morphologically, they are characterized by a diffuse red colour with no rapid motions. The main aim of this paper is to analyse two hitherto ignored aurorae that were observed at two low-latitude sites, Tenerife (28°N 18°W) and

Context. Most of the contribution to dust emission in clusters of galaxies comes from late-type galaxies. However, several ejection processes of material from these galaxies could introduce dust in the intracluster media. Even a relatively low abundance of this dust could act as an efficient cooling agent and have a relevant role in the evolution

We examine the impact of discrete numbers of stars in stellar populations on the results of Chemical Evolution Models. We explore the resulting dispersion in the true yields and their possible relation with the dispersion in observational data based on a Simple Closed-Box model. In this framework we find that the dispersion is larger for the less