Several authors have claimed that less luminous active galactic nuclei (AGNs) are not capable of sustaining a dusty torus structure. Thus, a gradual resizing of the torus is expected when the AGN luminosity decreases. Our aim is to examine mid-infrared observations of local AGNs of different luminosities for the gradual resizing and disappearance

Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aims: We investigate the scientific potential and

Context. Since CoRoT observations unveiled the very low amplitude modes that form a flat plateau in the power spectrum structure of δ Scuti stars, the nature of this phenomenon, including the possibility of spurious signals due to the light curve analysis, has been a matter of long-standing scientific debate. Aims: We contribute to this debate by

Since the 1995 discovery of the first exoplanet orbiting a solar-type star (Mayor & Queloz 1995), the number of these has grown exponentially. To date, more than 4,500 planets have been detected (more than 3,200 confirmed). In addition, the size of these planets is very diverse, from giant Jupiter-type planets (the first to be discovered) to Earth

We present C and O abundances in the Magellanic Clouds derived from deep spectra of H II regions. The data have been taken with the Ultraviolet-Visual Echelle Spectrograph at the 8.2-m Very Large Telescope. The sample comprises five H II regions in the Large Magellanic Cloud (LMC) and four in the Small Magellanic Cloud (SMC). We measure pure

Planetary nebulae are traditionally considered to represent the final evolutionary stage of all intermediate-mass stars (∼0.7-8 M⊙). Recent evidence seems to contradict this picture. In particular, since the launch of the Hubble Space Telescope, it has been clear that planetary nebulae display a wide range of striking morphologies that cannot be