Figure 1: Artist’s impression of a giant planet/brown dwarf.
Brown dwarfs are substellar objects with roughly 13 to 80 times the mass of Jupiter. These objects are not massive enough to burn hydrogen in their cores and they span the gap between giant planets and low-mass stars. Bouchy et al. (2015) present the detection of five brown dwarfs with minimum masses between 32 and 83 times the mass of Jupiter. These brown dwarfs orbit Sun-like stars with orbital periods longer than 10 years, and they were detected through radial velocity measurements of Sun-like stars over a relatively long period of roughly 20 years. This discovery doubles the number of known brown dwarfs with orbital periods longer than 10 years.
Figure 2: Radial velocity curve of HD10844, a F8V star with 0.98 times the mass of the Sun, located about 170 light years away. The brown dwarf orbiting it has at least 83 times the mass of Jupiter, and its orbit has a period of 32 years and an eccentricity of 0.57. With a minimum mass close to the boundary between the most massive brown dwarfs and the least massive stars, the brown dwarf around HD10844 is quite likely a star and not a brown dwarf at all. Bouchy et al. (2015)
Figure 3: Radial velocity of HD14348, a F5V star with 1.20 times the mass of the Sun, located about 185 light years away. The brown dwarf orbiting it has at least 49 times the mass of Jupiter, and its orbit has a period of 13.0 years and an eccentricity of 0.46. Bouchy et al. (2015)
Figure 4: Radial velocity of HD18757, a G4V star with 0.88 times the mass of the Sun, located only about 80 light years away. The brown dwarf orbiting it has at least 35 times the mass of Jupiter, and its orbit has a period of 109 years and a large eccentricity of 0.94. Its highly elongated orbit brings the brown dwarf from as close as 1.27 AU to as far as 43.1 AU from its host star. At closest approach, the brown dwarf receives close to the same intensity of insolation from its host star as what Earth receives from the Sun. Bouchy et al. (2015)
Figure 5: Radial velocity of HD72946, a G5V star with 0.96 times the mass of the Sun, located about 85 light years away. The brown dwarf orbiting it has at least 60 times the mass of Jupiter, and its orbit has a period of 15.9 years and an eccentricity of 0.50. Bouchy et al. (2015)
Figure 6: Radial velocity of HD209262, a G5V star with 1.02 times the mass of the Sun, located about 160 light years away. The brown dwarf orbiting it has at least 32 times the mass of Jupiter, and its orbit has a period of 14.9 years and an eccentricity of 0.35. Bouchy et al. (2015)
Reference:
Bouchy et al. (2015), “The SOPHIE search for northern extrasolar planets VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions”, arXiv:1511.08397 [astro-ph.SR]