An 8 month monitoring campaign on the Seyfert 1 galaxy Fairall 9 has been conducted with the International Ultraviolet Explorer in an attempt to obtain reliable estimates of continuum-continuum and continuum--emission-line delays for a high-luminosity active galactic nucleus (AGN). While the results of this campaign are more ambiguous than those of

Results from a multiwaveband study of the γ-ray-bright compact radio source 3C 454.3 are presented.

The discovery of hundreths of X-ray emitting stars possibly associated with pre-main sequence (PMS) low-mass stars far from molecular clouds, makes it necessary to adopt quantitative spectroscopic criteria for classifying them. T Tauri stars have young ages (

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A method for studying the full star formation history (SFH) of nearby galaxies,as a function of time, has been developped and implemented. For the first time, the full SFH of a nearby dwarf irregular galaxy (DIG) has been retrieved from the photometry of its resolved stars. NGC~6822 has been observed in $UBVRI$ at the 2.5m INT telescope, at the

A method for studying the star formation history (SFH) of nearby galaxies, as a function of time, has been developped and implemented. For the first time, the full SFH of a nearby dwarf irregular galaxy (DIG) has been retrieved from the photometry of its resolved stars. In the [(V-I),I] colour-magnitude diagram (CMD) of about 18000 stars in NGC