# Gliese 86

Gliese 86
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Eridanus
Gliese 86 A
Right ascension 02h 10m 25.93s[1]
Declination −50° 49′ 25.4″[1]
Apparent magnitude (V) 6.17[2]
Gliese 86 B
Right ascension 02h 10m 26s
Declination −50° 49′ 25″
Apparent magnitude (V)
Characteristics
Spectral type K1V / D?
U−B color index 0.45
B−V color index 0.812[1]
V−R color index 0.45
R−I color index 0.40
Astrometry
Proper motion (μ) RA: 2092.86 ± 0.27[1] mas/yr
Dec.: 653.21 ± 0.30[1] mas/yr
Parallax (π) 92.74 ± 0.32[1] mas
Distance 35.2 ± 0.1 ly
(10.78 ± 0.04 pc)
Details
Mass 0.79 M
Luminosity (bolometric) 0.47[note 1] L
Temperature 5188 K
Metallicity [Fe/H] = -0.24
Rotation 31 days
Age 2.4 × 109[3] years
Other designations
13 G. Eridani, GJ 86, HD 13445, HIP 10138, HR 637, SAO 232658
Database references
Exoplanet Archive data
ARICNS data
Extrasolar Planets
Encyclopaedia
data

Gliese 86 (13 G. Eridani) 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.[4]

## Stellar components

The primary companion (Gliese 86 A) is a K-type main-sequence star of spectral type K1V. The characteristics in comparison to our Sun are 79% the mass, 86% 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.[5] It was discovered in 2001 and initially suspected to be a brown dwarf,[6] 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.[7] Assuming the white dwarf has a mass about half that of our 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.[8]

## Planetary system

The preliminary astrometric measurements made with the Hipparcos space probe suggest the planet has an orbital inclination of 164.0° and a mass 15 times Jupiter, which would make the object a brown dwarf.[9] However, further analysis suggests the Hipparcos measurements are not precise enough to reliably determine astrometric orbits of substellar companions, thus the orbital inclination and true mass of the candidate planet remain unknown.[10] It was discovered by the Swiss 1.2 m Leonhard Euler Telescope operated by the Geneva Observatory.[11]

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 planetary system[12]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
b >3.91 ± 0.32 MJ 0.1130 ± 0.0065 15.76491 ± 0.00039 0.0416 ± 0.0072

## Notes

1. ^ From $\begin{smallmatrix}L=4 \pi R^2 \sigma T_{\rm eff}^4 \end{smallmatrix}$, where $\begin{smallmatrix}L \end{smallmatrix}$ is the luminosity, $\begin{smallmatrix}R \end{smallmatrix}$ is the radius, $\begin{smallmatrix}T_{\rm eff}\end{smallmatrix}$ is the effective surface temperature and $\begin{smallmatrix}\sigma \end{smallmatrix}$ is the Stefan–Boltzmann constant

## References

1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
2. ^ C. Cincunegui and P. J. D. Mauas (2004). "Library of flux-calibrated echelle spectra of southern late-type dwarfs with different activity levels". Astronomy and Astrophysics 414 (2): 699–706. Bibcode:2004A&A...414..699C. doi:10.1051/0004-6361:20031671.
3. ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal 687 (2): 1264–1293. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785.
4. ^ "Extrasolar Planet in Double Star System Discovered from La Silla" (Press release). Garching, Germany: European Southern Observatory. November 24, 1998. Retrieved December 29, 2012.
5. ^ Raghavan et al.; Henry, Todd J.; Mason, Brian D.; Subasavage, John P.; Jao, Wei‐Chun; Beaulieu, Thom D.; Hambly, Nigel C. (2006). "Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems". The Astrophysical Journal 646 (1): 523–542. arXiv:astro-ph/0603836. Bibcode:2006ApJ...646..523R. doi:10.1086/504823.
6. ^
7. ^ Mugrauer, M. and Neuhäuser, R. (2005). "Gl86B: a white dwarf orbits an exoplanet host star". Monthly Notices of the Royal Astronomical Society: Letters 361 (1): L15–L19. arXiv:astro-ph/0506311. Bibcode:2005MNRAS.361L..15M. doi:10.1111/j.1745-3933.2005.00055.x.
8. ^ Lagrange, A.-M. et al. (2006). "New constrains on Gliese 86 B. VLT near infrared coronographic imaging survey of planetary hosts". Astronomy and Astrophysics 459 (3): 955–963. Bibcode:2006A&A...459..955L. doi:10.1051/0004-6361:20054710.
9. ^ Han et al.; Black, David C.; Gatewood, George (2001). "Preliminary astrometric masses for proposed extrasolar planetary companions". The Astrophysical Journal Letters 548 (1): L57–L60. Bibcode:2001ApJ...548L..57H. doi:10.1086/318927.
10. ^ Pourbaix, D. and Arenou, F. (2001). "Screening the Hipparcos-based astrometric orbits of sub-stellar objects". Astronomy and Astrophysics 372 (3): 935–944. arXiv:astro-ph/0104412. Bibcode:2001A&A...372..935P. doi:10.1051/0004-6361:20010597.
11. ^ http://obswww.unige.ch/~udry/planet/coralie.html
12. ^ Butler, R. P. et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701.