Simultaneous multifrequency observations of the Seyfert 1 galaxy NGC 4051 : constant optical-infrared emission observed during large-amplitude X-ray variability.
Done, C.; Fabian, A. C.; Wamsteker, W.; Ward, M. J.; Lawrence, A.; Kunieda, H.; Tsuruta, S.; Smith, M. G.
United States, United Kingdom, Japan
Abstract
We report simultaneous infrared, optical, ultraviolet and X-ray observations of the low-luminosity Seyfert 1 galaxy, NGC 4051. A new method of reduction was developed to correct the optical flux for atmospheric variations due to seeing and extinction. The X-ray flux varied by factors of up to 2 on time-scales of tens of minutes whilst the optical flux remained steady to within 1 per cent. Our results rule out all models, including Compton scattering and synchrotron models, in which a single electron population is responsible for the formation of both the infrared- to-optical and the X-ray spectra. The optical emission region must be an order of magnitude larger than, or completely separate from, the X-ray source.