2017A&A...602A..58J -
Astronomy and Astrophysics, volume 602A58-58 (2017/6-1)
An eccentric companion at the edge of the brown dwarf desert orbiting the 2.4 M☉ giant star HIP 67537.
JONES M.I., BRAHM R., WITTENMYER R.A., DRASS H., JENKINS J.S., MELO C.H.F., VOS J. and ROJO P.
Abstract (from CDS):
We report the discovery of a substellar companion around the giant star HIP 67537. Based on precision radial velocity measurements from CHIRON and FEROS high-resolution spectroscopic data, we derived the following orbital elements for HIP 67537 b: mbsini=11.1+0.4–1.1Mjup, a=4.9+0.14–0.13AU and e=0.59+0.05–0.02. Considering random inclination angles, this object has ≥65% probability to be above the theoretical deuterium-burning limit, thus it is one of the few known objects in the planet to brown-dwarf (BD) transition region. In addition, we analyzed the HIPPARCOS astrometric data of this star, from which we derived a minimum inclination angle for the companion of ∼2°. This value corresponds to an upper mass limit of ∼0.3M☉, therefore the probability that HIP 67537 b is stellar in nature is ≤7%. The large mass of the host star and the high orbital eccentricity makes HIP 67537 b a very interesting and rare substellar object. This is the second candidate companion in the brown dwarf desert detected in the sample of intermediate-mass stars targeted by the EXoPlanets aRound Evolved StarS (EXPRESS) radial velocity program, which corresponds to a detection fraction of f=+2.0–0.5%. This value is larger than the fraction observed in solar-type stars, providing new observational evidence of an enhanced formation efficiency of massive substellar companions in massive disks. Finally, we speculate about different formation channels for this object.
Abstract Copyright:
© ESO, 2017
Journal keyword(s):
planetary systems - astrometry - techniques: radial velocities - techniques: spectroscopic - techniques: spectroscopic
Simbad objects:
6
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