Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distribution of the off-nuclear X-ray sources, interpreted by Zezas et al. as evidence of an association with a young stellar population. Our independent analysis of archive X-ray (Chandra) and optical (INT and HST) observations confirms the anisotropy of the X-ray sources but conducts to a different int...

We study accretion onto the neutron star in Be/X-ray binaries, using a 3D SPH code and the data imported from a high resolution simulation by Okazaki et al. (2002) for a coplanar system with a short period (Porb = 24.3 d) and moderate eccentricity (e = 0.34). We find that a timedependent accretion disk is formed around the neutron star in Be/X-ray binaries. The disk shrinks after the periastron...

We investigate models for the class of ultraluminous non–nuclear X–ray sources (ULXs) seen in a number of galaxies and probably associated with star–forming regions. Models where the X–ray emission is assumed to be isotropic run into several difficulties. In particular formation of sufficient numbers of the required ultramassive black–hole X–ray binaries is problematic, and the likely transient...

We report on recent progress in our theoretical understanding of X-ray binaries, which has largely been driven by new observations, and illustrate the interplay between theory and observations considering as examples intermediate-mass X-ray binaries, irradiation-driven evolution, ultraluminous X-ray sources and neutron stars with low-velocity kicks.

Context. Wolf Rayet/black hole binaries are believed to exist as a later evolutionary product of high-mass X-ray binaries. Hundreds of such binaries may exist in galaxies, but only a few of them are close enough to be observed as X-ray binaries. Only a couple of candidates have been reported so far. Aims. Based on XMM-Newton observations, we report the positional coincidence of the brightest X-...

I shall briefly review the observational properties of radio-emitting jets from Galactic X-ray binaries in relation with other wavebands: infrared, optical and X-ray. Special attention is paid to recent results obtained with the Spitzer Space Telescope on quiescent black holes as well as ultra-compact neutron star X-ray binaries.