Spectral optical monitoring of 3C390.3 in 1995-2007: I. Light curves and
  flux variation of the continuum and broad lines
  Here we present the results of the long-term (1995-2007) spectral monitoring
of the broad line radio galaxy \object{3C~390.3}, a well known AGN with the
double peaked broad emission lines, usually assumed to be emitted from an
accretion disk. To explore dimensions and structure of the BLR, we analyze the
light curves of the broad H$\alpha$ and H$\beta$ line fluxes and the continuum
flux. In order to find changes in the BLR, we analyze the H$\alpha$ and
H$\beta$ line profiles, as well as the change in the line profiles during the
monitoring period. First we try to find a periodicity in the continuum and
H$\beta$ light curves, finding that there is a good chance for quasi-periodical
oscillations. Using the line shapes and their characteristics (as e.g. peaks
separation and their intensity ratio, or FWHM) of broad H$\beta$ and H$\alpha$
lines, we discuss the structure of the BLR. Also, we cross-correlate the
continuum flux with H$\beta$ and H$\alpha$ lines to find dimensions of the BLR.
We found that during the monitoring period the broad emission component of the
H$\alpha$ and H$\beta$ lines, and the continuum flux varied by a factor of
$\approx $4-5. Also, we detected different structure in the line profiles of
H$\alpha$ and H$\beta$. It seems that an additional central component is
present and superposed to the disk emission. In the period of high activity
(after 2002), H$\beta$ became broader than H$\alpha$ and red wing of H$\beta$
was higher than the one of H$\alpha$. We found time lags of $\sim$95 days
between the continuum and H$\beta$ flux, and about 120 days between the
continuum and H$\alpha$ flux. Variation in the line profiles, as well as
correlation between the line and continuum flux during the monitoring period is
in the favor of the disk origin of the broad lines with the possible
contribution of some additional region and/or some kind of perturbation in the
disk.
