Markarian 6 nucleus since 1992

We present results of an optical spectral monitoring campaign of the Seyfert galaxy Markarian 6 for a period of nearly 6 years between 1992 January and 1997 November carried out with a CCD spectrograph at the 2.6 m Shajn Telescope of the Crimean Astrophysical Observatory. Our data set consists of 104 H beta region spectra and 56 H alpha region spectra. Light curves for H alpha and H beta emission lines, and the continuum at two bands near these lines, are given. The continuum variations are generally smooth and very pronounced. The H beta emission line is found to respond to continuum variations with a time lag of 18 +/- 2 days. The H alpha line has a similar lag. The continuum variations at 5170 and 7030 Angstrom are tightly correlated, pointing to no evidence for changes in the nonstellar continuum color in optics. A lag of about 5 days between these two continuum bands is suspected. The blue wing lags behind the red wing, ruling out a radial outflow in the broad-line region (BLR) and, in particular, the biconical outflow as responsible for the bumps in the broad-line profiles. We find that some changes in the profile shapes of Balmer emission lines in Mrk 6 are related to neither the matter redistribution nor the reverberation effects, but probably are driven by the changes in the anisotropy of the ionizing radiation. The H beta emission-line profile at V-r = +/- 3000 km s(-1) and the optical continuum show a well-correlated variability (with a lag), while the poor correlation for the profile segment at V-r = + 1300 km s(-1) can indicate the presence of two components in the broad-line profiles. One of the components has a double-peaked structure and is associated with the well-known blue bump observed in the Balmer profiles in Mrk 6.