Gliese 229

Gliese 229

Gliese 229 A and B.
Observation data Epoch J2000      Equinox J2000
Constellation	Lepus
Right ascension	06^h 10^m 34.6154^s[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
Distance	18.8 ± 0.1 ly (5.75 ± 0.03 pc)
Absolute magnitude (MV)	9.33[5]
Absolute bolometric magnitude (Mbol)	7.96[6]
Details
Mass	0.58/0.002[7] M☉
Radius	0.69/0.047[8] R☉
Luminosity (bolometric)	0.052[nb 1] L☉
Luminosity (visual, LV)	0.0158[nb 2]/0.00032 L☉
Temperature	3,700[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
SIMBAD	The 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. Perryman, M. A. C.; et al. (1997). "The Hipparcos Catalogue". Astronomy and Astrophysics 323: L49–L52. Bibcode:1997A&A...323L..49P.
2. 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. 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. 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. 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. 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 $\scriptstyle \frac{L_{V_{\ast}}}{L_{V_{\odot}}}=10^{0.4\left(M_{V_{\odot}} - M_{V_{\ast}}\right)}$

External links

• Brown dwarfs (NASA)