Multifrequency observation of the optically violent variable quasar 3C 446

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Abstract

Extensive optical and radio monitoring data and seven multifrequency spectra were obtained of the violently variable quasar 3C 446. The monitoring data suggest a correlation between the radio and optical outbursts, with the optical flare preceding the radio activity by 400-600 days. A difference in the statistical behavior of the optical and radio variability indicates that considerable processing occurs to the optical emitting plasma before it becomes radio emitting plasma. Within the radio band, outbursts proceed from high to low frequencies. An outburst in 1983 showed greater and more rapid variation in the optical than in the near-IR region. The 10-100 micron fluxes did not follow the higher frequency variation, suggesting a time delay between these spectral domains. During another time, the X-ray emission varied on a time scale of days and more rapidly than the UV or optical emission. On a time scale of weeks-months, the X-ray fluxes are well correlated with the UV-IR fluxes but not with the radio fluxes. The multifrequency data show that the flat radio spectrum turns over at 3-10 x 10^11^ Hz and the continuum steepens with frequency; α(IR) = -1.1, α(opt-UV) = -2 to -3. The X-ray emission lies an order of magnitude above an extrapolation of the optical-UV spectrum and has a harder spectrum. The power is primarily concentrated in the submillimeter and infrared region. When the source is faint, a blue bump may be present. The flux in the Lyα line is proportional to the UV continuum flux density when the source is bright but is independent of the continuum level when the source is faint. The data suggest that the X-rays are produced by the inverse Compton process from an emitting region (10^16^ cm) smaller than but related to the synchrotron emitting UV-IR region. The characteristic size of the emitting region increases with decreasing frequency from 10^16^ (X-ray region) to 1-3 x 10^17^ cm (far IR-submillimeter region) to 10^19^-10^20^ cm (radio region). Plasma conditions are best constrained at the frequency when the source becomes transparent, the far IR-submillimeter band, where B ~ 3-100 G, n ~ 40-100 cm^-3^; and the Doppler boosting factor δ ~ 1-5.

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