Connection between X-ray and optical variability in NGC 4151 |
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Authors: | V L Oknyanskij |
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Institution: | (1) Shternberg State Astronomical Institute, Moscow, Russia |
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Abstract: | We have used long light curves in the X-ray (ARIEL V, EXOSAT, Ginga and others), UV (IUE), and optical (data of intensive ground-based monitoring) ranges of NGC 4151 to investigate connections between variations in these spectral fields. Applying Fourier (CLEAN algorithm) and modern cross-correlation analysis, we revealed the different character of the variability and the cross-correlation between high and low states of the nucleus. In contrast to earlier results, we found that X-ray and optical fluxes correlate in the active state without any apparent delay.In the power spectrum of the optical and X-ray light curves in the high state we found the existence of the same period of about 65 days, which disappeared in the low state .We confirmed previous data that X-ray variations correlate more strongly with UV and optical continuum variability during the low state , but it is possible that the optical variations appear to lag behind those involving X-rays by several tens of days.Strong variations in H line profile and Fe X] 6374 line intensity variations correlate with the observed X-ray covering dip in 1990 (Yaqoobet al., 1993).We discuss briefly the implications of these results. |
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