We present optical spectroscopic observations of three Ultra Luminous X-ray sources (ULXs). Two of them are very close to the active galaxy NGC 720 and the other is near NGC 1073. The two around NGC 720 turn out to be quasars at z= 2.216 and z= 0.959, the one near NGC 1073 seems to be associated to an HII region at the redshift of NGC 1073. We

We present U, B, V, I (SUSI@NTT) and J, Ks (SOFI@NTT) photometry of the Large Magellanic Cloud (LMC) cluster Reticulum. The observing strategy and data reduction (DAOPHOTII/ALLFRAME) allowed us to reach an accuracy of the order of 0.01 - 0.03 mag in all the bands at limiting magnitudes typical of RR Lyrae stars. Reticulum hosts a sizable sample of

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High-resolution spectra of 30 late-type and 9 early-type candidate members of the young (˜50-80 Myr) open clusters NGC 2451 A and B have been analyzed in order to complement our previous photometric and X-ray study. Cluster membership of these X-ray selected stars has been confirmed or rejected on the basis of radial velocity and Hα chromospheric

The Rees-Sciama effect produced in mergers of galaxy clusters is discussed, and an analytical approximation to compute this effect from numerical simulations is given. Using this approximation and a novel model describing the physics of the merger, we characterize the spatial properties and symmetries of the Rees-Sciama signal. Based on these

We present a method for the analysis of latitude distribution associated with temperature and/or velocity perturbations of the stellar surface due to non-radial pulsation (NRP) modes in rapidly rotating B stars. The technique is applied together with Fourier Doppler Imaging (FDI) to high resolution and high signal-to-noise ratio spectroscopic