Variability is a key property of ultracool dwarfs as it may induce physical noise that limits the accuracy of radial velocities. In this paper we report on our current activities in the study of variability in ultracool dwarfs.

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The CCD UBV(RI)C observations of this paper have been made exclusively with the 0.84-m f/15 Ritchey-Chretien telescope at SPM, during the night of 2001 June 25/26 for the open cluster Be 80, and the nights 2002 February 6/7 and 8/9 for the clusters NGC 2192 and Be 15, respectively. (3 data files).

We numerically investigate the excitation and temporal evolution of oscillations in a two-dimensional coronal arcade by including the three-dimensional propagation of perturbations. The time evolution of impulsively generated perturbations is studied by solving the linear, ideal magnetohydrodynamic (MHD) equations in the zero-β approximation. As we

Context. The origin of carbon-enhanced metal-poor stars enriched with both s and r elements is highly debated. Detailed abundances of these types of stars are crucial to understand the nature of their progenitors. Aims: The aim of this investigation is to study in detail the abundances of SDSS J1349-0229, SDSS J0912+0216 and SDSS J1036+1212, three