SPECTROSCOPIC MONITORING OF ACTIVE GALACTIC NUCLEI .2. THE SEYFERT-1 GALAXY NGC-3516

We present results of a five month spectroscopic monitoring campaign of the Seyfert-1 galaxy NGC 3516. Using a new calibration method and applying a correction for seeing differences during the various observations we can scale the spectra to each other with a much higher accuracy than hitherto achieved. NGC 3516 shows large amplitude variations on a time scale of several weeks. Asymmetric profile variations occur on the same time scale as the continuum variations. We show the presence of a varying dip on the blue wing of the Hbeta profile, which is not present on the Halpha profile, and which corresponds to the absorption features previously seen in the UV emission lines of NGC 3516. From cross-correlation analysis we find a time lag of 14 +/- 2 days for the Halpha and 7 +/- 3 days for the Hbeta emission-line response to continuum variations.