Astron. J., 134, 749-758 (2007/August-0)
The mass of the candidate exoplanet companion to HD 33636 from Hubble Space Telescope astrometry and high-precision radial velocities.
BEAN J.L., McARTHUR B.E., BENEDICT G.F., HARRISON T.E., BIZYAEV D., NELAN E. and SMITH V.V.
Abstract (from CDS):
We have determined a dynamical mass for the companion to HD 33636 that indicates it is a low-mass star instead of an exoplanet. Our result is based on an analysis of Hubble Space Telescope (HST) astrometry and ground-based radial velocity data. We have obtained high-cadence radial velocity measurements spanning 1.3 yr of HD 33636 with the Hobby-Eberly Telescope at McDonald Observatory. We combined these data with previously published velocities to create a data set that spans 9 yr. We used this data set to search for, and place mass limits on, the existence of additional companions in the HD 33636 system. Our high-precision astrometric observations of the system with the HST Fine Guidance Sensor 1r span 1.2 yr. We simultaneously modeled the radial velocity and astrometry data to determine the parallax, proper motion, and perturbation orbit parameters of HD 33636. Our derived parallax, πabs=35.6±0.2 mas, agrees within the uncertainties with the Hipparcos value. We find a perturbation period P=2117.3±0.8 days, semimajor axis aA=14.2±0.2 mas, and system inclination i=4.1°±0.1°. Assuming the mass of the primary star to be MA=1.02±0.03 M☉, we obtain a companion mass MB=142±11 MJup=0.14±0.01 M☉. The much larger true mass of the companion relative to its minimum mass estimated from the spectroscopic orbit parameters (Msini=9.3 MJup) is due to the nearly face-on orbit orientation. This result demonstrates the value of follow-up astrometric observations to determine the true masses of exoplanet candidates detected with the radial velocity method.
Astrometry - Stars: Planetary Systems - Stars: Distances - stars: individual (HD 33636) - Techniques: Interferometric - Techniques: Radial Velocities
Reference stars from tables 4 and 5 not found in UCAC catalogue, not in SIMBAD.
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