SIMBAD references

The light curve of Mrk 6 for 1970-2002 is presented and discussed. The amplitudes of variability were 1.6^m, 1.1^m, and 0.8^m in UBV bands, respectively. The magnitudes of the underlying galaxy in the 27.5'' aperture were found to be U_g=15.82, B_g=15.42 and V_g=14.36. The mean color indices of the variable component are (U-B)_var=-0.49 and (B-V)_var=0.75 without correction for reddening. In the time intervals from 10 days to 1300 days the structure function can be presented as a power function, SF∝τ^b, where b=0.72±0.04. The time where the SF for Mrk 6 reaches the upper plateau is about 3300 days. The observed SF can be interpreted by the superposition of independent flares model with the maximal duration of flares ∼800 days. If these flares are located in the radiation pressure dominated region of the accretion disk, the size of this region is about 70, 330R_S, assuming the viscous parameter α is 0.1, 0.01, respectively. It is concluded that the optical long-term variability of Seyfert galaxies can be explained by thermal instability in the accretion disk.