We present low-resolution (R=900) optical (576.1-1051.1 nm) spectroscopic observations of 40 candidate very low mass members in the Upper Scorpius OB association. These objects were selected using the I, J, and K photometry available in the Deep Near-Infrared Survey (DENIS) database. We have derived spectral types, and we have measured Hα and Na I

In a recent preprint, Pepper et al. (2002) evaluate the sensitivity of photon-noise limited transit searches for habitable planets. They conclude that these searches have the largest chance of success if they are optimized toward the surveying of M stars. Such an optimisation implies several constraints and trade-offs. The principal one is that M

We present preliminary results from an ongoing study of the bulges of S0 galaxies. We show that in a subsample of 14 barred S0 galaxies, fully half the photometrically defined bulges show kinematic signatures of "pseudobulges" -- that is, their kinematics are dominated by rotation. In four of these galaxies, we identify at least two subcomponents

In this paper we establish a necessary condition for the application of stellar population synthesis models to observed star clusters. Such a condition is expressed by the requirement that the total luminosity of the cluster modeled be larger than the contribution of the most luminous star included in the assumed isochrones, which is referred to as

We report optical spectroscopic observations of a sample of 6 low-galactic latitude microquasar candidates selected by cross-identification of X-ray and radio point source catalogs for |bII | ≤ 5 °. Two objects resulted to be of clear extragalactic origin, as an obvious cosmologic redshift has been measured from their emission lines. For the rest

The space debris population in low Earth orbits (LEO) has been extensively studied during the last decade and reasonable models covering all size ranges were produced. Information on the distribution of objects in the geostationary ring (GEO), however, is still comparatively sparse. Until quite recently the population of man-made objects in GEO had