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T.A. Rector (NOAO), J.T. Stocke (CASA - Colorado)
BL Lacertae objects are an extreme class of AGN which are believed to be highly beamed radio galaxies. However there is evidence that not all BL Lacs agree with this simple picture. In particular, an excess of MgII absorption systems along BL Lac sightlines suggests that gravitational lensing may be another means of creating the BL Lac phenomenon; and indeed many BL Lacs show evidence of lensing. However, lensing has been confirmed in only one BL Lac: 1Jy 0218+357. This was accomplished by discovering its compact radio ``Einstein ring", a telltale signature of lensing. However it is not yet known if 0218+357 is merely an oddity, or if lensed sources occur in BL Lac samples in significant numbers. If so, their presence can affect the interpretation of AGN unification models under consideration.
We present deep, high-resolution VLA A--array images of seven lensing candidates from the 1Jy BL Lac sample which have unusually compact or distorted radio morphologies. These multi-wavelength observations are intended to better resolve these sources determine whether or not these objects are indeed lensed. If lensed, the multiple images of each source component will have identical spectral indices.