15 Sagittae - 15 Sagittae B

15 Sagittae B is a high-mass substellar L dwarf of spectral class L4 ± 1.5, only a few Jupiter masses below the limit for stars, in a long-period orbit around the primary star. Imaged by the Keck telescope, was the first brown dwarf candidate orbiting a sun-like star detected via imaging and is currently the only known companion brown dwarf which both has a significant radial velocity trend on the primary that has also been imaged.

The brown dwarf was originally thought to have a semi-major axis of 14 AU and a circular orbit viewed from pole-on, but ten more years of observations found that the brown dwarf's orbit is viewed from nearly edge-on, is significantly eccentric and appeared to be moving in a circular orbit when first discovered, but is now approaching the primary as viewed from Earth.

Companion Mass
Radius
Luminosity
Temperature
Orbital
period
Semimajor
axis
Orbital
ecc.
Inclination
Discovery
year
B 68.7+2.4
−3.1
1.0 ± 0.4 0.000075
1510-1850 73.3+2.2
−3.9
18.3+0.4
−0.5
0.50
97.3 +0.4
−0.5
2002

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