The contribution to population in ellipticals of blue stragglers: A test of their origin

An observational test of the binary hypothesis for the origin of the blue straggler (BS) stars has been performed y searching for radial velocity variables among 27 BS in five galactic clusters. The significance of the BS phenomenon for the interpretation of evolutionary synthesis models and the spectra of elliptical galaxies is briefly discussed.     

Hot Subdwarfs: Magnetic, Oscillatory and Other Physical Properties

Hot subdwarf stars (hot sds) are blue subluminous objects. Only a few determinations areavailable to date regarding the study of such aspects as rotation,microturbulent velocities or the magnetic nature of these objects. Over26 sdBs are known to date to be multiperiodic rapid oscillators. Thisproject presents preliminary results of new observations and models of asample of pulsating and non-pulsating hot sds, includingconsiderations on mass loss and eventual magnetic properties.     

Photometric Studies of O-type Hot Subdwarfs

We present a photometric study of eight sdOs and one sdOB on which simultaneous photometry in four Strömgren filters was performed. Our study seeks to detect the possible pulsators among the candidates.     

Optical Classification of IRAS Post-AGB Candidates

We present the first results of a survey carried out on a sample of optically bright post-AGB candidates selected from the IRAS Point Source Catalogue, many of them previously unidentified in the literature. The selection criteria are based on their characteristic far infrared colours. Low resolution spectroscopy of more than 150 sources has been obtained during 6 years. Our preliminary analysis confirms that most of the candidates observed are true post-AGB stars, some of them still strongly reddened. Some young planetary nebulae, a few young stellar objects and active galactic nuclei are also present in the sample. The distribution of post-AGB stars with different spectral types in the IRAS two-colour diagram and its evolutionary implications are briefly discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Closer View of the Nucleus of NGC 4314

We present a high-resolution kinematical study of the ionized gas in the circumnuclear region of NGC 4314. Our spectra reveal the presence of a central structure (apparently a ring or torus) located at ∼ 2 arcsec from the nucleus, which we identify as the shocked interface between the nuclear bar and the gas inside the HII region ring. This revised version was published online in July 2006 with corrections to the Cover Date.