Desde el espacio exterior llegan constantemente a la Tierra gran cantidad de particulas cargadas, la mayoria protones, aunque algunas veces tambien llegan nucleos atomicos que pueden ser tan masivos como el hierro. El espectro de estas particulas abarca un rango muy amplio de energia y sigue una ley de potencias. Este espectro plantea el problema

Aims: One of the most striking features predicted by standard models of galaxy formation is the presence of anti-correlations in the matter distribution on large enough scales (r > r_c). Simple arguments show that the location of the length scale r_c, marking the transition from positive to negative correlations, is the same for any class of

We present a chemical abundance analysis based on high resolution UVES spectra of seventeen bright giant stars in the Globular Cluster (GC) M 22. We obtained an average iron abundance of [Fe/H] = -1.76±0.02 (internal errors only) and an α enhancement of 0.36±0.04 (internal errors only). Na and O, and Al and O follow the well known anticorrelations

Context: The knowledge of the initial mass function (IMF) in open clusters constitutes one way of constraining the formation of low-mass stars and brown dwarfs, along with the frequency of multiple systems and the properties of disks. Aims: The aim of the project is to determine the shape of the mass function in the low-mass and substellar regimes

After an outburst that lasted more than 2.3 years (starting around June 12th., 2007; Palmer et al., ATel #1113), the neutron star transient and atoll source 4U 1608-52 has returned to quiescence. The source was last detected by Swift-BAT, RXTE-PCA and RXTE-ASM on September 14th. (~0.006 BAT c/s/cm2), September 19th. (~3.5 mCrab) and October 5th. (