Astronomy and Astrophysics the Extreme High Frequency Peaked Bl Lac 1517+656
نویسندگان
چکیده
We present optical spectroscopy data that allowed a measurement of the redshift for the X-ray selected BL Lacertae object 1517+656. With a redshift of z = 0.702 this object has an absolute magnitude of M B = −26.4 and is also an extremely powerful radio and X-ray source. Although being a high frequency peaked BL Lac, this object is one of the most luminous BL Lac objects known so far. Being also a candidate for gravitational lensing, this object is of high interest for the BL Lac research. Assuming several cosmological models and a realistic redshift for the lensed object, we find that 1517+656 has a mass > 2 · 10 12 M ⊙ and a high velocity dispersion > 350 km sec −1 .
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