We present a wide field study of the Globular Clusters/Low Mass X-ray Binary (LMXB) connection in the giant elliptical NGC1399. The large FOV of the ACS/WFC, combined with the HST and Chandra high resolution, allow us to constrain the LMXB formation
scenarios in elliptical galaxies. We confirm that NGC1399 has the highest LMXB fraction in GCs of all nearby elliptical galaxies studied so far, even though the exact value depends on galactocentric distance due to the interplay of a differential GC vs galaxy light distribution and the GC color dependence. In fact LMXBs are preferentially hosted by bright, red GCs out to $>5 R_{eff}$ of the galaxy light. The finding that GC hosting LMXBs follow the radial distribution of their parent GC population, argues against the hypothesis that the external dynamical influence of the galaxy affects LMXB formation in GCs. On the other hand field LMXBs closely match the host galaxy light, thus indicating that they are originally formed in situ and not inside GCs. We measure GC structural parameters, finding that the LMXB formation likelihood is influenced independently by mass, metallicity and GCs structural parameters. In particular the GC central density plays a major role in predicting which GC host accreting binaries. Finally our analysis shows that LMXBs in GCs are marginally brighter than those in the field, and in particular the only color-confirmed GC with $L_X>10^{39}$ erg s$^{-1}$ shows no variability, which may indicate a superposition of multiple LMXBs in these systems.
The Wide Field X-ray Telescope (WFXT) is a proposed mission with a high survey speed, due to the combination of large field of view (FOV) and effective area, i.e. grasp, and sharp PSF across the whole FOV. These characteristics make it suitable to de
tect a large number of variable and transient X-ray sources during its operating lifetime. Here we present estimates of the WFXT capabilities in the time domain, allowing to study the variability of thousand of AGNs with significant detail, as well as to constrain the rates and properties of hundreds of distant, faint and/or rare objects such as X-ray Flashes/faint GRBs, Tidal Disruption Events, ULXs, Type-I bursts etc. The planned WFXT extragalactic surveys will thus allow to trace variable and transient X-ray populations over large cosmological volumes.
We list here the contents of the Proceedings of the Wide Field X-ray Telescope conference held in Bologna, Italy on 25-26 Nov 2009. The conference highlighted the scientific potential and discovery space provided by an X-ray mission concept character
ized by a wide field-of-view (1 sq.deg.), large effective area (1 sq.mt.) and approximately constant PSF (~5 arcsec HEW) across the whole FOV. The index is in html form with clickable links to the individual contributions.
We present a wide field study of the Globular Clusters/Low Mass X-ray Binaries connection in the cD elliptical NGC1399, combining HST/ACS and Chandra high resolution data. We find evidence that LMXB formation likelihood is influenced by GCs structura
l parameters, in addition to the well known effects of mass and metallicity, independently from galactocentric distance.
