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A Highly Eccentric Brown Dwarf around a Giant Star

29 Sep 2014, 10:00 UTC
A Highly Eccentric Brown Dwarf around a Giant Star
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To date, ~10 brown dwarfs are known around giant stars (i.e. evolved stars). Brown dwarf are objects more massive than planets, but are not massive enough to count as full-fledged stars. M. I. Jones et al. (2014) report on the discovery of a brown dwarf on a highly eccentric orbit around the giant star HIP 97233. The brown dwarf, identified as HIP 97233 b, has an orbital period of 1058.8 days and a minimum mass of 20 times the mass of Jupiter.With an orbital eccentricity of 0.61, HIP 97233 b is the brown dwarf with the most eccentric orbit known around a giant star. The mass and orbit of HIP 97233 b were both determined from the gravitational “tugging” it exerts on its host star which was observed in the form of a radial velocity signature (i.e. Doppler shifts in the star’s spectral lines).Figure 1: Artist’s impression of a giant planet. Figure 2: Upper panel: Radial velocity curve for the host star of HIP 97233 b. Lower panel: Residuals from the best fit. M. I. Jones et al. (2014).HIP 97233 b highly eccentric orbit takes it from as near as 1.0 AU to as far as 4.1 AU from its ...

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