Gliese 86

Gliese 86 (13 G. Eridani, HD 13445) is a K-type main-sequence star approximately 35 light-years away in the constellation of Eridanus. It has been confirmed that a white dwarf orbits the primary star. In 1998 the European Southern Observatory announced that an extrasolar planet was orbiting the star.^[12]

Gliese 86

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Eridanus
Gliese 86 A
Right ascension	02h 10m 25.9191s[1]
Declination	−50° 49′ 25.467″[1]
Apparent magnitude (V)	6.17[2]
Gliese 86 B
Right ascension	02h 10m 26s[citation needed]
Declination	−50° 49′ 2″[citation needed]
Characteristics
Spectral type	K1V[3] + DQ6[4][5]
U−B color index	0.45
B−V color index	0.812[6]
V−R color index	0.45
R−I color index	0.40
Astrometry
Radial velocity (Rv)	56.7[7] km/s
Proper motion (μ)	RA: 2,124.853±0.075[1] mas/yr Dec.: 638.092±0.063[1] mas/yr
Parallax (π)	92.7042±0.0454 mas[1]
Distance	35.18 ± 0.02 ly (10.787 ± 0.005 pc)
Absolute magnitude (MV)	5.95[8]
Orbit[4]
Primary	Gliese 86 A
Companion	Gliese 86 B
Period (P)	≈100 yr
Semi-major axis (a)	23.7 au
Eccentricity (e)	0.429
Inclination (i)	126.44°
Longitude of the node (Ω)	234.2°
Details[9]
Gliese 86 A
Mass	0.83±0.05 M☉
Radius	0.79±0.03 R☉
Surface gravity (log g)	4.56±0.10 cgs
Temperature	5180±80 K
Metallicity [Fe/H]	−0.27±0.07 dex
Rotational velocity (v sin i)	2.0±1.0 km/s
Age	10±1 Gyr
Gliese 86 B
Mass	0.5425[4] M☉
Temperature	8180±120[5] K
Other designations
Gliese 86A: CD−51°532, HD 13445, HIP 10138, HR 637, SAO 232658, WDS J02104-5049A[10]
Gliese 86B: GJ 86 B, HD 13445B, WDS J02104-5049B, WD 0208-510[11]
Database references
SIMBAD	data
Exoplanet Archive	data
ARICNS	data

Stellar components

The primary companion (Gliese 86 A) is a K-type main-sequence star of spectral type K1V. The characteristics in comparison to the Sun are 83% the mass, 79% the radius, and 50% the luminosity. The star has a close-orbiting massive Jovian planet.

Gliese 86 B is a white dwarf located around 21 AU from the primary star, making the Gliese 86 system one of the tightest binaries known to host an extrasolar planet.^[13] It was discovered in 2001 and initially suspected to be a brown dwarf,^[14] but high contrast observations in 2005 suggested that the object is probably a white dwarf, as its spectrum does not exhibit molecular absorption features which are typical of brown dwarfs.^[15] Assuming the white dwarf has a mass about half that of the Sun and that the linear trend observed in radial velocity measurements is due to Gliese 86 B, a plausible orbit for this star around Gliese 86 A has a semimajor axis of 18.42 AU and an eccentricity of 0.3974.^[16] When both stars were on the main sequence, the separation between the two stars was closer, at around 9 AU.^[4] More precise measurements for the white dwarf give it a mass of 55% the mass of the Sun^[4] and a temperature of around 8200 K.^[9]

Planetary system

The planet Gliese 86 b was discovered by the Swiss 1.2 m Leonhard Euler Telescope operated by the Geneva Observatory.^[17] Such an object was formed from a protoplanetary disk that was truncated at 2 AU from the parent star.^[4]

The radial velocity measurements of Gliese 86 show a linear trend once the motion due to this planet are taken out. This may be associated with the orbital motion of the white dwarf companion.

The Gliese 86 A planetary system^[18]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥6.588±0.018 MJ	0.114340±0.000001	15.76480±0.00004	0.048±0.002	—	—

See also

• List of exoplanets discovered before 2000 - Gliese 86b