The JEM-X Signal Multiplexing Systems are large HURA codes "written" in a pure tungsten plate 0.5 mm thick. 24.247 hexagonal pixels (25% open) are spread over a total area of 535 mm diameter. The tungsten plate is embedded in a mechanical structure formed by a Ti ring, a pretensioning system (Cu-Be) and an exoskeleton structure that provides the

We present new optical - near-IR spectroscopic and photometric observations of the newly discovered galactic microquasar LS 5039, which indicate a classification for the mass donor in the system of O6.5V((f)). Optical spectroscopy and photometry shows no variability over a timescale of years, and we find no evidence of modulation by, or emission

This paper addresses some questions which have arisen from the use of the Sérsic r1/n law in modelling the luminosity profiles of early-type galaxies. The first issue deals with the trend between the half-light radius and the structural parameter n. We show that the correlation between these two parameters is not only real, but also a natural

The detection of 1.809 MeV gamma-ray line emission from the Vela region by the COMPTEL telescope presents a direct prove of recent nucleosynthesis activity in this region. It has been suggested that the observed 1.809 MeV emisson could arise from the radioactive decay of 26Al produced by the Vela SNR and/or the nearby Wolf-Rayet star γ2 Vel

Results from a new multi-wavelength evolutionary synthesis model including the γ-ray line emission from various radioactive isotopes (26Al, 60Fe) are presented. In particular the predicted γ-ray line observations combined with measurements of ionising fluxes can efficiently constrain the age of a stellar population, and help to identify the primary

M31 has been monitored by a Chandra GTO program, which used both the HRC and ACIS from 1999 to 2001 and a GO program, which used ACIS-S during 2000-2001. We report here the lightcurves of X-ray sources in M31 during the past two years. X-ray sources in M31, like in our Galaxy, exhibit variability on long timescales (days to months). Some sources