CCD photometry of the BL Lacertae objects 1218+304, 1219+28, and 1727+50 - Point sources, associated nebulosity, and broad-band spectra

Visual and far-red surface photometry has been obtained for the X-ray emitting BL Lacertae objects 1218+304 and 1727+50, and the highly variable object 1219+28. The intensity distribution for 1727+50 can be modeled by means of a central point source and a de Vaucouleurs intensity law for an underlying galaxy. The spectral index of the point source of 1727+50 is found to be 0.97, while the indices for 1218+304 and 1219+28 are 0.91 and 1.7, respectively. Comparison of the results presented with X-ray and radio-frequency observations suggests that all emission from 1727+50 and 1218+304 is due to direct synchrotron emission. If this is the case, the relativistic motion effects and continuous particle injection are also implied by the data.