The Continuum of BL Lac

Multichannel-scanner observations from 5820 to 10860 A, polarization observations from 4700 to 7980 A, and photoelectric UB V observations have been obtained for the star BL Lac. The red and infrared continuum is smooth and has a steep slope P(v) ~ p~2.78. UBV observations show excess in the ultraviolet. The continuum is highly polarized, and the polarization is constant in the wavelength range observed. These results can be explained if the major portion of the continuum of BL Lac is of synchrotron origin. Further, identification of the radio source VRO 42.22.01 with BL Lac can be taken to confirm the non-thermal nature of the continuum of BL Lac