Abstract
ABSTRACTWe have resolved Kelu‐1 into a binary system with a separation of ∼290 mas using the Laser Guide Star Adaptive Optics system on the Keck II telescope. We have also reanalyzed a 1998 HST observation of Kelu‐1 and find that the observed PSF is best fit by a binary object separated by 45 mas. Observations at multiple epochs confirm that the two objects share a common proper motion and clearly demonstrate the first evidence of orbital motion. Kelu‐1B is fainter than Kelu‐1A by 0.39 ± 0.01 mag in the K′ filter and 0.50 ± 0.01 mag in the H filter. We derive spectral types of L 2 ± 1 and L 3.5 ± 1 for Kelu‐1A and B, respectively. The separation of flux into the two components rectifies Kelu‐1’s overluminosity problem, which has been known for quite some time. Given the available data, we are able to constrain the inclination of the system to >81° and the orbital period to ≳40 yr.
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