We calculate the emissivity for the direct URCA process in strongly magnetized, degenerate matter in neutron stars, under beta -equilibrium. We show that, if the magnetic field is large enough for protons and electrons to be confined to their ground Landau levels, the field-free threshold condition on proton concentration no longer holds, and

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An analysis is performed of multicolour observations of OJ 287 carried out during the OJ-94 Project. It is found that in the optical region the variable sources have the same power-law spectrum (F_nu ~ nu (-1.5) ) irrespective of flux level. In the IR the spectrum flattens during the flare possibly because of synchrotron self-absorption. The

The synthetic color-magnitude diagram (CMD) methodology to study the star formation history (SFH) of nearby galaxies is briefly reviewed. Firstly the most significant features of the CMD for this task are discussed. Then, the procedure of computing synthetic CMDs is explained and the main results obtained by our group in the last few years

We present results on the star formation history of the Local Group dSph galaxy Leo I, obtained through the analysis of its deep HST color-magnitude diagram (CMD) using model CMDs computed from stellar evolutionary models. Our results show unambiguously that Leo I experienced a major increase of its star formation rate from about 6 Gyr ago to 2 Gyr

In this paper we analyse the structure of a small sample of galaxies using a set of CCD images in standard photometric bands presented in a previous paper (del Rio & Cepa 1998a, hereafter cite{p2}). The galaxies are NGC 157, 753, 895, 4321, 6764, 6814, 6951, 7479 and 7723, and the selected bands were B and I. Seven galaxies are grand design, i.e