These properties are widely attributed to relativistic beaming of synchrotron radiation emitted by the relativistic jets which power the large-scale double radio sources associated with many ordinary quasars. Presumably blazars also have a similar thermal component which is usually hidden by the Doppler-boosted synchrotron continuum whilst normal quasars also have a synchrotron beam. However, relatively little attention has been paid to the emission line properties of blazars. In particular, the aim of this programme is to determine whether or not the highly anisotropic radiation field associated with the relativistic jet has an important effect on the properties of the broad emission lines. Two observational programmes have been initiated to address this question.
First results are inconclusive.
A new development is the extensive multi-wavelength observing campaign which has been put in hand to follow up the recent discovery of a broad Ha line in BL Lacertae. A spectropolarimetric survey of compact radio source quasars is also envisaged. The models will be used to explore the effects of the beam on the line profiles and their variability characteristics, and more generally, to predict emission line equivalent width distributions for populations of randomly oriented sources.