Issue |
A&A
Volume 528, April 2011
|
|
---|---|---|
Article Number | L8 | |
Number of page(s) | 4 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361/201116533 | |
Published online | 25 February 2011 |
Letters to the Editor
HD 5388 b is a 69 MJup companion instead of a planet
Observatoire de Genève, Université de Genève,
51 chemin des Maillettes,
1290
Sauverny,
Switzerland
e-mail: johannes.sahlmann@unige.ch
Received:
18
January
2011
Accepted:
8
February
2011
We examined six exoplanet host stars with non-standard Hipparcos astrometric solution,
which may be indicative of unrecognised orbital motion. Using Hipparcos intermediate
astrometric data, we detected the astrometric orbit of HD 5388 at a significance level of
99.4% (2.7 σ). HD 5388 is a metal-deficient star and hosts a planet
candidate with a minimum mass of 1.96 MJ discovered in 2010.
We determined its orbit inclination to be and
the corresponding mass of its companion HD 5388 b
to be M2 = 69 ± 20 MJ. The orbit
is seen almost face-on and the companion mass lies at the upper end of the brown-dwarf
mass range. A mass lower than 13 MJ was excluded at the
3 σ-level. The astrometric motions of the five other stars had been
investigated by other authors revealing two planetary companions, one stellar companion,
and two statistically insignificant orbits. We conclude that HD 5388 b is not a planet but
most likely a brown-dwarf companion. In addition, we find that the inclinations of the
stellar rotation axis and the companion’s orbital axis differ significantly.
Key words: stars: individual: HD 5388 / planetary systems / brown dwarfs / astrometry
© ESO, 2011
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