Optical Spectral Variability of NGC 4151 during 1990статья

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[1] Oknyanskij V. L., van Groningen E. Optical spectral variability of ngc 4151 during 1990 // Astronomical and Astrophysical Transactions. — 1997. — Vol. 14, no. 2. — P. 105–118. We use the intensive optical spectral monitoring of NGC 4151 obtained during the LAG campaign in January - June 1990, to investigate the profile and intensity variations of H and H emission lines. The continuum light curve values were supplemented with photoelectrical photometry (11 dates) obtained at the Crimean observatory of the Sternberg Astronomical Institute by V. M. Lyuty. Cross-correlation analysis shows that the time delay between continuum changes and variability of H and H is about 4 ± 2 days. The error in the delay was found by applying cross-correlation analysis to a model series, with the same temporal distribution, power spectrum, and signal-to-noise ratio as the actual data. This value of time delay is much lower than was found in other papers for other epochs. We can note two variabilly components in these changes in the lines: one fast and one slow. The amplitude of the slow component relative to the fast component is higher for H then for H. The year 1990 was peculiar for NGC 4151 because the object returned to the state which was typical before 1980. The very strong dip in the covering factor was deduced from X-ray observations for the first half of 1990. During this interval interesting peaks were observed in the red wings of H and H, which were previously observed very rarely. The same peak was seen in the UV line CIV during the first half of 1990. Intensities of the peaks changed in correlation with the continuum and line variability. We noted some differences in the behaviors of these peaks in H and H. The results obtained are briefly discussed.

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