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Session 78 - Seyfert Galaxies.
Display session, Friday, January 09
We report the first results of an 11 month HST/FOS monitoring campaign of the broad emission-line region in the Seyfert 1 nucleus NGC 3516. During the campaign the UV continuum showed a factor of 5 variation; correspondingly the strongest broad UV emission-lines (e.g. Ly\alpha, CIV) displayed a somewhat weaker, though still significant variation (a factor of 2). In contrast, no variation was detected in either the strong broad MgII emission-line or in the many strong blended lines of FeII from \lambda\lambda 2200--3400ÅP>While historically the flux in the broad MgII emission-line has varied (a factor of 2 within a few years), the profile shape has remained unchanged for at least a decade. In contrast, the high ionization lines (HILs, e.g. Ly\alpha, CIV) show both emission-line flux and profile changes on relatively short timescales, which appear to be correlated with changes in the continuum level. Differences between the rms and steady-state profiles of the HILs suggests that the variable component originates in a distinct (both spatially and kinematically) region of the BLR. Significantly, on Feb 21st 1996, the profile shapes of the HILs and MgII were identical. This suggests that the non-variable component of these lines either (a) arises from the same cloud population, or (b) is formed in self-similar structures (e.g. a terminal wind).
Program listing for Friday