Gliese 229

Gliese 229

Gliese 229 A and B.
Observation data
Epoch J2000      Equinox J2000
Constellation Lepus
Right ascension 06h 10m 34.6154s[1]
Declination −21° 51′ 52.715″[1]
Apparent magnitude (V) 8.14
Characteristics
Spectral type M1Ve/T7[2]
U−B color index +1.222[2]
B−V color index +1.478[2]
Variable type Flare star
Astrometry
Radial velocity (Rv)+3.9[3] km/s
Proper motion (μ) RA: –137.01[1] mas/yr
Dec.: –714.05[1] mas/yr
Parallax (π)173.81 ± 0.99[4] mas
Distance18.8 ± 0.1 ly
(5.75 ± 0.03 pc)
Absolute magnitude (MV)9.33[5]
Absolute bolometric
magnitude (Mbol)		7.96[6]
Details
Mass0.58/0.002[7] M☉
Radius0.69/0.047[8] R☉
Luminosity (bolometric)0.052[nb 1] L☉
Luminosity (visual, LV)0.0158[nb 2]/0.00032 L☉
Temperature3,700[6] K
Rotational velocity (v sin i)1[9] km/s
Other designations
BD-21°1377, HD 42581, HIP 29295, LHS 1827, NSV 2863, SAO 171334, TYC 5945- 765-1
Database references
SIMBADThe system
A
B

Gliese 229 (also written as Gl 229 or GJ 229) is a red dwarf about 19 light years away in the constellation Lepus. It has 58% of the mass of the Sun,[7] 69% of the Sun's radius,[8] and a very low projected rotation velocity of 1 km/s at the stellar equator.[9]

The star is known to be a low activity flare star, which means it undergoes random increases in luminosity because of magnetic activity at the surface. The spectrum shows emission lines of calcium in the H and K bands. The emission of X-rays has been detected from the corona of this star.[10] These may be caused by magnetic loops interacting with the gas of the star's outer atmosphere. No large-scale star spot activity has been detected.[2]

The space velocity components of this star are U = +12, V = –11 and W = –12 km/s.[11] The orbit of this star through the Milky Way galaxy has an eccentricity of 0.07 and an orbital inclination of 0.005.[2]

Substellar companions

A substellar companion was discovered in 1994 and confirmed in 1995 as Gliese 229B,[12][13] one of the first two instances of clear evidence for a brown dwarf, along with Teide 1. Although too small to sustain hydrogen-burning nuclear fusion as in a main sequence star, with a mass of 20 to 50 times that of Jupiter (0.02 to 0.05 solar masses), it is still too massive to be a planet. As a brown dwarf, its core temperature is high enough to initiate the fusion of deuterium with a proton to form helium-3, but it is thought that it used up all its deuterium fuel long ago.[14] This object now has a surface temperature of 950 K.[15]

In March 2014, a super-Neptune mass planet candidate was announced in a much closer-in orbit around GJ 229 ([16]). Given the proximity to the Sun, the orbit of GJ 229b might be fully characterized by the Gaia space-astrometry mission or via direct imaging.

The Gliese 229 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
GJ 229Ab >32 M⊕ 0.97 471 <0.32 — —
GJ 229B <80 MJ >35 >10000 — — —

References

  1. 1 2 3 4 Perryman, M. A. C.; et al. (1997). "The Hipparcos Catalogue". Astronomy and Astrophysics 323: L49–L52. Bibcode:1997A&A...323L..49P.
  2. 1 2 3 4 5 Byrne, P. B.; Doyle, J. G.; Menzies, J. W. (May 1, 1985). "Optical photometry and spectroscopy of the flare star Gliese 229 (=HD42581)". Monthly Notices of the Royal Astronomical Society 214: 119–130. Bibcode:1985MNRAS.214..119B. doi:10.1093/mnras/214.2.119.
  3. ↑ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Retrieved 2009-10-19.
  4. ↑ Perryman; et al. (1997). "HIP 29295". The Hipparcos and Tycho Catalogues. Retrieved 2014-11-29.
  5. ↑ "The One Hundred Nearest Star Systems". RECONS. Georgia State University. January 1, 2012. Retrieved 2013-04-16.
  6. 1 2 Morales, J. C.; Ribas, I.; Jordi, C. (February 2008). "The effect of activity on stellar temperatures and radii". Astronomy and Astrophysics 478 (2): 507–512. arXiv:0711.3523. Bibcode:2008A&A...478..507M. doi:10.1051/0004-6361:20078324. Data from CDS table J/A+A/478/507.
  7. 1 2 Zechmeister, M.; Kürster, M.; Endl, M. (October 2009). "The M dwarf planet search programme at the ESO VLT + UVES. A search for terrestrial planets in the habitable zone of M dwarfs". Astronomy and Astrophysics 505 (2): 859–871. arXiv:0908.0944. Bibcode:2009A&A...505..859Z. doi:10.1051/0004-6361/200912479.
  8. 1 2 White, Stephen M.; Jackson, Peter D.; Kundu, Mukul R. (December 1989). "A VLA survey of nearby flare stars". Astrophysical Journal Supplement Series 71: 895–904. Bibcode:1989ApJS...71..895W. doi:10.1086/191401.
  9. 1 2 Reiners, A. (May 2007). "The narrowest M-dwarf line profiles and the rotation-activity connection at very slow rotation". Astronomy and Astrophysics 467 (1): 259–268. arXiv:astro-ph/0702634. Bibcode:2007A&A...467..259R. doi:10.1051/0004-6361:20066991.
  10. ↑ Schmitt JHMM, Fleming TA, Giampapa MS (September 1995). "The X-Ray View of the Low-Mass Stars in the Solar Neighborhood". Ap J. 450 (9): 392–400. Bibcode:1995ApJ...450..392S. doi:10.1086/176149.
  11. ↑ Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg. Bibcode:1969VeARI..22....1G.
  12. ↑ "Astronomers Announce First Clear Evidence of a Brown Dwarf". Space Telescope Science Institute news release STScI-1995-48. November 29, 1995. Retrieved 24 September 2013.
  13. ↑ Oppenheimer, Ben R. (2014), "Companions of Stars: From Other Stars to Brown Dwarfs to Planets and the Discovery of the First Methane Brown Dwarf", in Joergens, Viki, 50 Years of Brown Dwarfs - From Prediction to Discovery to Forefront of Research, Astrophysics and Space Science Library 401, Springer, pp. 81–111, ISBN 978-3-319-01162-2
  14. ↑ J. Kelly Beatty; Carolyn Collins Petersen; Andrew Chaikin (1999). The New Solar System. Cambridge University Press.
  15. ↑ Geißler, K.; Chauvin, G.; Sterzik, M. F. (March 2008). "Mid-infrared imaging of brown dwarfs in binary systems". Astronomy and Astrophysics 480 (1): 193–198. arXiv:0712.1887. Bibcode:2008A&A...480..193G. doi:10.1051/0004-6361:20078229.
  16. ↑ Tuomi, Mikko; et al. "Bayesian search for low-mass planets around nearby M dwarfs – Estimates for occurrence rate based on global detectability statistics". Monthly Notices of the Royal Astronomical Society. in press. arXiv:1403.0430. Bibcode:2014MNRAS.441.1545T. doi:10.1093/mnras/stu358.

Notes

  1. ↑ Using the absolute bolometric magnitude of Gliese 229 A \scriptstyle M_{bol_{\ast}}=7.96 and the absolute bolometric magnitude of the Sun \scriptstyle M_{bol_{\odot}}=4.74, the bolometric luminosity can be calculated by \scriptstyle \frac{L_{bol_{\ast}}}{L_{bol_{\odot}}}=10^{0.4\left(M_{bol_{\odot}} - M_{bol_{\ast}}\right)}
  2. ↑ Using the absolute visual magnitude of Gliese 229 A \scriptstyle M_{V_{\ast}}=9.33 and the absolute visual magnitude of the Sun \scriptstyle M_{V_{\odot}}=4.83, the visual luminosity can be calculated by \scriptstyle \frac{L_{V_{\ast}}}{L_{V_{\odot}}}=10^{0.4\left(M_{V_{\odot}} - M_{V_{\ast}}\right)}

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