Optical spectrophotometry of the active galaxy PKS 0521-365 over a period of 7 years is reported, together with the analysis of IUE archival spectra. The Hα emission line intensity varied by more than a factor of 2 during the monitoring. Similar amplitude variations are observed in the optical and UV continuum, which however are not simply

The discovery of Li in the late type secondary of the black hole binary V404 Cyg has motivated considerable interest in the presence of this light element in stars orbiting compact objects in general. We report here on a search for Li in cataclysmic binaries (CVs), where a low mass star transfers mass onto a white dwarf. For this purpose, we have

We study the delay induced by gravitational light bending in the arrival times of signals emitted by an anisotropic source in rotation (pulsar). The shift of the direction of the allowed pulsar beam (a vector defined by the null geodesic connecting the pulsar to the observer) with orbital phase induces a delay arising from the movement of the

Extensive infrared observations were taken of OJ 287 in 1993/94 as part of an on-going monitoring campaign of this object started in 1988. The data show that this blazar reached very high levels in the infrared in Fall'94 after a continuous increase in brightness through the winter and spring of 1993/94. The infrared fluxes registered at maximum

A magnetic flux tube anchored at the bottom of the solar convection zone and rising toward the surface as a result of an undulatory instability can be affected by a sudden catastrophic expansion and weakening of the magnetic field at its apex if the original field strength is below a few times 104 G. Such an "explosion" occurs if the flux tube

We have measured the ^12^C/^13^C interstellar ratio in the Coalsack, a prominent dark nebula in the southern sky, by means of high resolution (λ/δλ=6x10^4^) observations of the λ4232A CH^+^ line in the direction of the star HD110432 (d=~0.31kpc). The collection of a total of 53 spectra of this star and of a reference bright star (α Vir) has allowed