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Description
We report the detections of a giant planet (MARVELS-7b) and a brown dwarf (BD) candidate (MARVELS-7c) around the primary star in the close binary system, HD87646. To the best of our knowledge, it is the first close binary system with more than one substellar circumprimary companion that has been discovered. The detection of this giant planet was accomplished using the first multi-object Doppler instrument (KeckET) at the Sloan Digital Sky Survey (SDSS) telescope. Subsequent radial velocity observations using the Exoplanet Tracker at the Kitt Peak National Observatory, the High Resolution Spectrograph at the Hobby Eberley telescope, the "Classic" spectrograph at the Automatic Spectroscopic Telescope at the Fairborn Observatory, and MARVELS from SDSS-III confirmed this giant planet discovery and revealed the existence of a long-period BD in this binary. HD87646 is a close binary with a separation of ~22 au between the two stars, estimated using the Hipparcos catalog and our newly acquired AO image from PALAO on the 200inch Hale Telescope at Palomar. The primary star in the binary, HD87646A, has T_eff_=5770+/-80K, logg=4.1+/-0.1, and [Fe/H]=-0.17+/-0.08. The derived minimum masses of the two substellar companions of HD87646A are 12.4+/-0.7M_Jup_ and 57.0+/-3.7M_Jup_. The periods are 13.481+/-0.001days and 674+/-4 days and the measured eccentricities are 0.05+/-0.02 and 0.50+/-0.02 respectively. Our dynamical simulations show that the system is stable if the binary orbit has a large semimajor axis and a low eccentricity, which can be verified with future astrometry observations.
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