Spectroscopic monitoring of active galactic nuclei. II - The Seyfert-1 galaxy NGC 3516

Wanders, I.; van Groningen, E.; Alloin, D.; Aretxaga, I.; Axon, D.; de Bruyn, A. G.; Clavel, J.; Dietrich, M.; Goad, M. R.; Gondhalekar, P.; Horne, K.; Jackson, N.; Kollatschny, W.; Laurikainen, E.; Lawrence, A.; Masegosa, J.; O'Brien, P. T.; del Olmo, A.; Penston, M. V.; Perea, J.; Perez, E.; Perez-Fournon, I.; Perry, J. J.; Robinson, A.; Rodriguez Espinosa, J. M.; Stirpe, G. M.; Tadhunter, C.; Terlevich, R.; Unger, S.; Wagner, S. J.; Williams, R.
Bibliographical reference

Astronomy and Astrophysics (ISSN 0004-6361), vol. 269, no. 1-2, p. 39-53.

Advertised on:
3
1993
Number of authors
31
IAC number of authors
1
Citations
55
Refereed citations
47
Description
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 H-beta profile, which is not present on the H-alpha 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 H-alpha and 7 +/- 3 days for the H-beta emission-line response to continuum variations.