Ultraviolet and X-ray observations of the BL Lac object MK 501.
Boksenberg, A.; Penston, M. V.; Snijders, M. A. J.; Barr, P.; Sanford, P. W.; Ives, J. C.
United Kingdom, Spain
Abstract
We present ultraviolet and X-ray satellite observations of Mk 501. The ultraviolet data after dereddening assuming E(B-V) = 0.11 show a power-law spectrum with α = 0.51+0.10-0.15. The visible and infrared fluxes are in good agreement with this power-law if the underlying elliptical galaxy has a luminosity MV = -22.4. Extrapolation of the ultraviolet power-law gives a good fit to the radio data for υ > 10GHz. Although the observations at different frequencies were not simultaneous, time variations large enough to affect our conclusions seem unlikely. The X-ray measurements show a powerlaw with α = 0.8±0.5 or bremsstrahlung with kT& gt; 6 keV, and we exclude self-Compton radiation from the low frequency (υ < 10GHz) radio component as the dominant mechanism for X-ray production. A possible alternative is self-Compton radiation from the 10 GHz to ultraviolet synchrotron source.