Abstract
BL LACERTAEobjects are extragalactic sources, generally of low redshift, with highly variable, strongly polarized continuum emission ranging from radio wavelengths to X-rays, but with little or no evidence of line emission. It has been suggested1that BL Lacs are in fact more distant radio-loud, optically violently variable (OVV) quasars whose continuum is enhanced, relative to the line emission, by gravitational lensing caused by a star in an intervening galaxy. I argue here, however, that the spectral similarity of BL Lacs and OWs over a wide wavelength range can be explained by gravitational lensing only if the continuum-emitting region is small, a requirement that is contradicted by independent observations.
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Gear, W. Are BL Lac objects too large to be gravitationally lensed?. Nature 349, 676–678 (1991). https://doi.org/10.1038/349676a0
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DOI: https://doi.org/10.1038/349676a0
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