The complex X-ray absorbers of NGC 3516 observed by BeppoSAX

In this paper we present the analysis of two broadband (0.1-150 keV) BeppoS AX observations of the Seyfert 1 galaxy NGC 3516. The two observations were taken 4 months apart, on 1996 November 8 and 1997 March 12. We report a dr amatic change in the degree of obscuration of the central source between th e two observations and propose, as possible explanations, transient absorpt ion by either a stationary-state cloud of cold gas crossing the line of sig ht or a varying-state, initially neutral and dense amount of expanding gas with decreasing density and therefore decreasing opacity. We also report th e detection of a second highly ionized absorber/emitter, which causes deep Fe XVII-XXII K edges at similar to7.8 keV to appear in both of the BeppoSAX spectra of NGC 3516 and possibly produces the soft X-ray continuum emissio n in the 1 keV blend of Fe L recombination lines detected during the epoch of heavy nuclear obscuration.