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We address in this work the general features of a possible compact stars composed by elementary fermions beyond the quark level. The {it locus} of these hypothetic objects in the mass-radius plane is constructed for the maximum mass (minimum radius) of the sequence of models in terms of a compositeness scale only, and in fact this approach applies for any composite model postulating fermions at or beyond the preon level. We point out a constraint on the preon mass arising from the applicability of the General Relativity structure equations, leading to the questioning of the hypothesis of light preons if the preon scale is high, provided classical compact objects are enforced. Some remarks on the existence of superdense stars of astrophysical and primordial origin are made and discussed.
An increasing fraction of carbon-enhanced metal-poor (CEMP) stars is found as their iron abundance, [Fe/H], decreases below [Fe/H] = -2.0. The CEMP-s stars have the highest absolute carbon abundances, [C/H], and are thought to owe their enrichment in
We present some of the strategies being developed to classify and parameterize objects obtained with spectra from the Sloan Digital Sky Survey (SDSS) and the RAdial Velocity Experiment (RAVE) and present some results. We estimate stellar atmospheric
Magnetism of 3d transition metals at high density has always received wide interest due to existence of magnetism at the core of the Earth. For ferromagnetic cobalt, although there is a theoretical prediction that its magnetic moment would vanish whe
The second supernova that forms double-neutron-star systems is expected to occur in a progenitor that is ultra-stripped due to binary interactions. Thus, the secondary neutron stars mass as well as the post-supernova binarys orbital parameters will d
We review the observational evidence for dust formation in Wolf-Rayet binary systems and in Type II Supernova ejecta. Existing theoretical models describing the condensation of solids in carbon-rich Wolf-Rayet stars and in Supernovae close by and at