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

We present photometric analysis and follow-up spectroscopy for a population of extremely red stellar objects extracted from the point-source catalogue of the Isaac Newton Telescope (INT) Photometric Hα Survey (IPHAS) of the northern Galactic plane. The vast majority of these objects have no previous identification. Analysis of optical, near- and