# DISCOVERY OF A FAINT COMPANION TO ALCOR USING MMT/AO 5 μm IMAGING

@article{Mamajek2010DISCOVERYOA,
title={DISCOVERY OF A FAINT COMPANION TO ALCOR USING MMT/AO 5 $\mu$m IMAGING},
author={Eric E. Mamajek and Matthew A. Kenworthy and Philip M. Hinz and Michael R. Meyer},
journal={The Astronomical Journal},
year={2010},
volume={139},
pages={919 - 925}
}
• Published 26 November 2009
• Physics
• The Astronomical Journal
We report the detection of a faint stellar companion to the famous nearby A5V star Alcor (80 UMa). The companion has M-band (λ = 4.8 μm) magnitude 8.8 and projected separation 1.″11 (28 AU) from Alcor. The companion is most likely a low-mass (∼0.3 M☉) active star which is responsible for Alcor's X-ray emission detected by ROSAT (LX ≃ 1028.3 erg s−1). Alcor is a nuclear member of the Ursa Major star cluster (UMa; d ≃ 25 pc, age ≃ 0.5 Gyr), and has been occasionally mentioned as a possible…
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