The nature of close companions of the BL Lac Objects 1ES 0502+675 and 1ES 1440+122

Abstract

We report on deep radio images and optical spectroscopy of two BL Lac objects that have very close compact companions. The two targets, 1ES 0502+675 and 1ES 1440+122, were selected from the HST imaging survey of 110 BL Lacs as candidates for possible gravitational lensing. The new observations clearly demonstrate that the companion objects are not secondary images of the active nuclei but, in spite of the relatively low chance projection probability, foreground Galactic stars. Gravitational lensing appears to be unimportant to the BL Lac phenomenon. We discuss the radio properties of the BL Lac objects in the context of standard beaming models, and show they are as expected for beamed FRI radio galaxies.

13 pages, 5 figures, ApJ in press

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• Normalization of the extragalactic background light from high-energy gamma-ray observations
• Probing cluster environments of blazars through gamma-gamma absorption