We have investigated the long term variability of the intensities of the broad-line region emission lines in the UV spectra of Seyfert I galaxy NGC 5548 from 1973-1996. We have obtained the following results: 1) a high level correlation between the intensities of emission lines as well as between intensities of emission lines and continuum uxes was discovered. With increasing wavelength the correlation in both cases becomes weaker, 2) the relationship between the intensity of emission lines and the ux radiation in the continuum can be expressed by a power law function with coefficients of α ≈ 0:8 - 1:1 for different lines. When the difference between the wavelengths of spectral lines and the continuum is increased, the value of the power function decreases, and 3) it was found that the magnitude of the variability of the line intensities are weaker than the range of variability of the continuum uxes. The magnitude of the variability of the line intensities and the continuum uxes increase at longer wavelengths.

ABSTRACT
1. INTRODUCTION
2. OBSERVATIONAL MATERIAL AND RESULTS
3. CONCLUSIONS
REFERENCES

• Nariman Z. Ismailov(Shamakhy Astrophysical Observatory of Azerbaijan National Academy of Sciences)
• Ulviyye Z. Bashirova(Shamakhy Astrophysical Observatory of Azerbaijan National Academy of Sciences)