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D. Kazanas, S. Nayakshin (NASA/GSFC, Code 661)
We test the ``reprocessing paradigm" for the optical -- UV variability of AGN, according to which the variability in this wavelength range is driven by a variable X-ray component, by providing detailed models of the correlated X-ray -- optical observations of NGC 3516 obtained in a recent multiwavelength campaign. To this end we compute the light curves at \lambda\lambda 3590 and 5510 Åusing as input the observed X-ray light curve and the response function appropriate to an infinitely thin disk with the X-ray source at a given height hx above it, as well as model X-ray reflection and ``standard" (optically thick, geometrically thin) accretion disk O-UV spectra, for two different values of the black hole mass (107, 108 M\odot). The form of the model optical light curves is quite different from those observed, despite the similarity of their amplitudes. The model light curves exhibit generally no lags between \lambda\lambda 3590 and 5510 Å, but the (unobserved) lags of ~2 days for M=108 M\odot between the X-ray and the optical emission, disfavor this range of the black hole mass. On the other hand, the X-ray reflection spectra favor a black hole mass M=108 M\odot, being strongly inconsistent with M=107 M\odot, with the spectral and timing models thus favoring different values of the black hole mass. Finally, the O-UV spectra are inconsistent with those obtained from ``standard" optically thick, geometrically thin accretion disks.
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