In this study we present the absolute magnitude calibrations of thin-disc main-sequence stars in the optical , and in the near-infrared . Thin-disc stars are identified by means of Padova isochrones, and absolute magnitudes for the sample are evaluated via the newly reduced Hipparcos data. The obtained calibrations cover a large range of spectral

Aims: We study in detail nine sources in the direction of the young σ Orionis cluster, which is considered to be a unique site for studying stellar and substellar formation. The nine sources were selected because of their peculiar properties, such as extremely-red infrared colours or excessively strong Hα emission for their blue optical colours

This contribution gives an overview of the ground-based observing efforts organized to collect the auxiliary data mandatory for the calibrations and tests of the Gaia data processing.

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En este trabajo estudiamos una muestra de galaxias infrarrojas luminosas y ultraluminosas a desplazamientos al rojo (z) entre 0.5 y 3, seleccionadas en el infrarrojo medio y para las que disponemos de espectroscopía infrarroja obtenida con el instrumento IRS a bordo del telescopio espacial infrarrojo Spitzer, además de fotometría en óptico e