ar X iv : a st ro - p h / 98 02 07 8 v 1 6 F eb 1 99 8 1 High energy properties of X – ray sources observed with BeppoSAX

ar X iv : a st ro - p h / 98 02 08 2 v 1 6 F eb 1 99 8 What is the True Covering Factor of Absorbing Matter in BALQSO ’ s ?

ar X iv : a st ro - p h / 98 11 14 9 v 1 1 0 N ov 1 99 8 The BeppoSAX High Energy Large Area Survey ( HELLAS )

We have surveyed ∼ 50 deg of sky in the largely unexplored 5-10 keV band using the BeppoSAX MECS instrument, finding 180 sources. After correction for the non uniform sky coverage we find about 18 sources deg with F5−10keV > ∼ 5 × 10 erg cm s , and resolve 30-40 % of the hard 5-10 keV Cosmic X-ray Background (XRB). Optical identification of a first small sample of sources show that most (11 out...

ar X iv : a st ro - p h / 98 02 02 8 v 1 3 F eb 1 99 8 Phase Transitions in Neutron Stars

Phase transitions in neutron stars due to formation of quark matter, kaon condensates, etc. are discussed with particular attention to the order of these transitions. Observational consequences of phase transitions in pulsar angular velocities are examined.

ar X iv : a st ro - p h / 98 02 06 3 v 1 5 F eb 1 99 8 The Redshift Distribution of Distant Sources from Gravitational Depletion in Clusters

Gravitational lensing can be used to analyze the redshift distribution of faint galaxies. In particular the magnification bias modifies locally the galaxy number density of lensed sources observed in lensing clusters. This depletion area probes the redshift distribution of galaxies beyond B = 25. In this proceedings I present this new tool to infer the redhsift distribution of faint galaxies.

ar X iv : a st ro - p h / 99 02 06 2 v 1 4 F eb 1 99 9 SOURCES OF RELATIVISTIC JETS IN THE GALAXY