Gliese 229

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Short description: Star in the constellation Lepus

Coordinates: Sky map 06h 10m 34.6154s, −21° 51′ 52.715″

Gliese 229
Gliese 229 is located in the constellation Lepus
Gliese 229 is located in the constellation Lepus
Gliese 229
Location of Gliese 229 in the constellation Lepus

Observation data
Equinox J2000.0]] (ICRS)
Constellation Lepus[1]
Right ascension  06h 10m 34.61494s[2]
Declination −21° 51′ 52.6564″[2]
Apparent magnitude (V) 8.12[3]
Characteristics
Red dwarf[4]
Spectral type M1Ve[5]
U−B color index +1.222[5]
B−V color index +1.478[5]
Variable type Flare star[5]
Brown dwarfs[6]
Spectral type T7+T8[6]
Astrometry
A
Radial velocity (Rv)+4.23±0.12[2] km/s
Proper motion (μ) RA: −135.692(11)[2] mas/yr
Dec.: −719.178(17)[2] mas/yr
Parallax (π)173.5740 ± 0.0170[2] mas
Distance18.791 ± 0.002 ly
(5.7612 ± 0.0006 pc)
Absolute magnitude (MV)9.326[7]
Absolute bolometric
magnitude (Mbol)		7.96[8]
Orbit[9]
PrimaryGliese 229 A
CompanionGliese 229 B
Period (P)349+37
−29 years
Semi-major axis (a)42.9+3.0
−2.4 astronomical unit|AU
Eccentricity (e)0.736+0.014
−0.011
Inclination (i)47.7+2.5
−2.9°
Longitude of the node (Ω)168.3+0.3
−0.4°
Periastron epoch (T)2,466,912+97
−63[7]
Argument of periastron (ω)
(secondary)		358.285+0.836
−0.846°
Semi-amplitude (K1)
(primary)		0.081674+0.001688
−0.001680[10] km/s
Orbit[9]
PrimaryGliese 229 Ba
CompanionGliese 229 Bb
Period (P)12.1343+0.0012
−0.0013 days
Semi-major axis (a)0.0424±0.0004 astronomical unit|AU[6]
Eccentricity (e)0.2306+0.0025
−0.0026
Inclination (i)31.4+0.5
−0.6°
Longitude of the node (Ω)210.4+1.5
−1.4°
Periastron epoch (T)2,460,378.38±0.04[6]
Argument of periastron (ω)
(secondary)		3.2±1.1°
Details
A
Mass0.581±0.007[9] M☉
Radius0.549±0.043[11] R☉
Luminosity (bolometric)0.0430[7] L☉
Surface gravity (log g)4.695±0.035[11] cgs
Temperature3,700[8] K
Metallicity−0.02±0.06[12]
Rotation28.9±1.6 d[13]
Rotational velocity (v sin i)1[14] km/s
Ba
Mass37.7±1.1[9] MJup
Radius0.81+0.05
−0.12[12] RJup
Luminosity (bolometric)3.890+0.375
−0.342×10−6[6] L☉
Surface gravity (log g)5.15±0.04[12] cgs
Temperature900+78
−29[12] K
Metallicity0.00+0.04
−0.03[12]
Age2.45±0.20[6] Gyr
Bb
Mass33.4±1.0[9] MJup
Radius0.85+0.12
−0.05[12] RJup
Luminosity (bolometric)2.630+0.254
−0.231×10−6[6] L☉
Surface gravity (log g)5.07+0.04
−0.011[12] cgs
Temperature775+20
−33[12] K
Metallicity0.00+0.04
−0.03[12]
Age2.45±0.20[6] Gyr
Other designations
NSV 2863, BD−21°1377, GJ 229, HD 42581, HIP 29295, SAO 171334, LHS 1827, TYC 5945-765-1[15]
Database references
SIMBADA
B
Exoplanet Archivedata

Gliese 229 (also written as Gl 229 or GJ 229) is a multiple system composed of a red dwarf and two brown dwarfs,[6][4] located 18.8 light years away in the constellation Lepus. The primary component has 58% of the mass of the Sun,[7] 55% of the Sun's radius,[11] and a very low projected rotation velocity of 1 km/s at the stellar equator.[14]

Red dwarf

File:GL229LightCurve.png
A light curve for Gliese 229 showing a small flare, adapted from Byrne et al. (1985)[5]

Gliese 229 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.[16] 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.[5]

The space velocity components of this star are U = +12, V = –11 and W = –12 km/s.[17] The orbit of this star through the Milky Way galaxy has an eccentricity of 0.07 and an orbital inclination of 0.29°.[18]

Brown dwarfs

Gliese 229 A and B

A substellar companion was discovered in 1994 by Caltech astronomers Kulkarni, Tadashi Nakajima, Keith Matthews, and Rebecca Oppenheimer, and Johns Hopkins scientists Sam Durrance and David Golimowski. It was confirmed in 1995 as Gliese 229B,[19][20] It was one of the first brown dwarfs discovered. Although too small to sustain hydrogen-burning nuclear fusion as in a main sequence star, with a mass of around 40 to 60 times that of Jupiter (0.06 solar masses),[10][21] 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.[22] This object has a surface temperature of 950 K.[23]

Gliese 229B is the prototype of the T-dwarfs, due to the detection of methane in its spectrum.[24] It also shows other molecules in its atmosphere, namely water vapor,[25] carbon monoxide[26] and ammonia.[27][12] Atomic absorption lines of caesium,[28] sodium and potassium are also detected.[29]

Gliese 229 B was later found to be a binary brown dwarf.[6] Since 2021 it was suggested to be an unresolved binary, given the inconsistency between the object's measured mass and luminosity.[7][30] Further evidence that Gliese 229B is an equal-mass binary comes from high-resolution spectroscopy from the Subaru Telescope.[31] Gliese 229 B was then finally resolved in 2024 with VLT/GRAVITY and VLT/CRIRES+. The components are called Gliese 229 Ba and Gliese 229 Bb. The pair is a tight orbit with an orbital period of 12.1 days and a semi-major axis of 0.042 astronomical units (about 16 Earth-Moon distances). The changes in radial velocity extracted from CRIRES+ helped to resolve the orbit of Gliese 229B. The binary has an inclination of 31.4°±0.3° and an eccentricity of 0.234±0.004. The inclination of the binary is misaligned by 37+7
−10° in respect to the orbit of Gliese 229B around Gliese 229A.[6] Additional radial velocity changes between two epochs were detected in Gliese 229B with Keck NIRSPEC. This team independently discovered the binarity of Gliese 229B.[4]

The brown dwarf pair was observed with JWST MIRI low resolution spectroscopy. Previous works showed a difference in abundances between host star and companion in Gliese 229 from near-infrared spectra. This new study using mid-infrared data showed that the pair has abundances consistent with the host star. The metallicities were measured to be C/O = 0.65±0.05 and [M/H]=0.00+0.04
−0.03 and are equal for each brown dwarf in the pair. The host star has C/O = 0.68±0.12 and [M/H] = −0.02±0.06.[12]

Search for planets

In March 2014, a super-Neptune mass planet candidate was announced in a much closer-in orbit around GJ 229.[32] Given the proximity of the Gliese 229 system to the Sun, the orbit of GJ 229 Ab might be fully characterized by the Gaia space-astrometry mission or via direct imaging. In 2020, a super-Earth mass planet was discovered around GJ 229. GJ 229 Ac orbits the star closer in than GJ 229 Ab, located towards the outer edge but still well inside the star's habitable zone and in that sense similar to Mars in our own Solar System. While considering GJ 229 Ab unconfirmed, the study estimated a significantly lower minimum mass for it.[33]

However, a more recent study found that when stellar activity was taken in account, the radial velocity signals corresponding to the planets' orbital periods disappeared. Therefore, intrinsic activity of the host star or errors in the previous observations are the cause of the radial velocity variations, instead of planets, which mean Gliese 229 Ab and Gliese 229 Ac likely do not exist.[13]

See also

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R  Constellation record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ Koen, C.; Kilkenny, D.; Van Wyk, F.; Marang, F. (2010). "UBV(RI)C JHK observations of Hipparcos-selected nearby stars". Monthly Notices of the Royal Astronomical Society 403 (4): 1949. doi:10.1111/j.1365-2966.2009.16182.x. Bibcode: 2010MNRAS.403.1949K. 
  4. ↑ 4.0 4.1 4.2 Whitebook, Samuel; Brandt, Timothy D.; Brandt, G. Mirek; Martin, Emily C. (2024-10-06). "Discovery of the Binarity of Gliese 229B, and Constraints on the System's Properties" (in en). The Astrophysical Journal Letters 974 (2): L30. doi:10.3847/2041-8213/ad7714. ISSN 2041-8205. Bibcode: 2024ApJ...974L..30W. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 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 (2): 119–130. doi:10.1093/mnras/214.2.119. Bibcode: 1985MNRAS.214..119B. 
  6. ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 Xuan, Jerry W.; Mérand, A.; Thompson, W.; Zhang, Y.; Lacour, S.; Blakely, D.; Mawet, D.; Oppenheimer, R. et al. (2024-10-16). "The cool brown dwarf Gliese 229 B is a close binary" (in en). Nature 634 (8036): 1070–1074. doi:10.1038/s41586-024-08064-x. ISSN 1476-4687. PMID 39415016. Bibcode: 2024Natur.634.1070X. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Brandt, G. Mirek; Dupuy, Trent J.; Li, Yiting; Chen, Minghan; Brandt, Timothy D.; Wong, Tin Long Sunny; Currie, Thayne; Bowler, Brendan P. et al. (2021). "Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3". The Astronomical Journal 162 (6): 301. doi:10.3847/1538-3881/ac273e. Bibcode: 2021AJ....162..301B. 
  8. ↑ 8.0 8.1 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. doi:10.1051/0004-6361:20078324. Bibcode: 2008A&A...478..507M.  Data from CDS table J/A+A/478/507 .
  9. ↑ 9.0 9.1 9.2 9.3 9.4 Thompson, William; Blakely, Dori; Xuan, Jerry W.; Bouchard-Côté, Alexandre; Bourdarot, Guillaume; Biron-Lattes, Miguel; Campbell, Trevor; Eisenhauer, Frank et al. (2025). "On the Orbit of the Binary Brown Dwarf Companion GL229 Ba and Bb". The Astronomical Journal 169 (4): 193. doi:10.3847/1538-3881/adb4f2. Bibcode: 2025AJ....169..193T. 
  10. ↑ 10.0 10.1 Feng, Fabo et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series 262 (21): 21. doi:10.3847/1538-4365/ac7e57. Bibcode: 2022ApJS..262...21F. 
  11. ↑ 11.0 11.1 11.2 Stassun, Keivan G.; Oelkers, Ryan J.; Paegert, Martin; Torres, Guillermo; Pepper, Joshua; De Lee, Nathan; Collins, Kevin; Latham, David W. et al. (2019-10-01). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal 158 (4): 138. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256. Bibcode: 2019AJ....158..138S. 
  12. ↑ 12.00 12.01 12.02 12.03 12.04 12.05 12.06 12.07 12.08 12.09 12.10 Xuan, Jerry W.; Perrin, Marshall D.; Mawet, Dimitri; Knutson, Heather A.; Mukherjee, Sagnick; Zhang, Yapeng; Hoch, Kielan K.; Wang, Jason J. et al. (2024-11-15). "Atmospheric abundances and bulk properties of the binary brown dwarf Gliese 229 Bab from JWST/MIRI spectroscopy". The Astrophysical Journal 977 (2): L32. doi:10.3847/2041-8213/ad92f9. Bibcode: 2024ApJ...977L..32X. 
  13. ↑ 13.0 13.1 Deslières, Ariane; Cadieux, Charles; Doyon, René; Artigau, Étienne; Cook, Neil J.; Fontanive, Clémence; Vandal, Thomas (February 2025). "The Gl 229 System Revisited with the Line-by-line Framework: Planetary Signals Now Appear as Stellar Activity Ghosts" (in en). The Astronomical Journal 169 (3): 182. doi:10.3847/1538-3881/ada77a. ISSN 1538-3881. Bibcode: 2025AJ....169..182D. 
  14. ↑ 14.0 14.1 Reiners, Ansgar (May 2007). "The narrowest M-dwarf line profiles and the rotation-activity connection at very slow rotation". Astronomy and Astrophysics 467 (1): 259–268. doi:10.1051/0004-6361:20066991. Bibcode: 2007A&A...467..259R. 
  15. ↑ "Gliese 229". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Gliese+229. 
  16. ↑ Schmitt JHMM; Fleming TA; Giampapa MS (September 1995). "The X-Ray View of the Low-Mass Stars in the Solar Neighborhood". Astrophys. J. 450 (9): 392–400. doi:10.1086/176149. Bibcode: 1995ApJ...450..392S. 
  17. ↑ Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg 22: 1. Bibcode: 1969VeARI..22....1G. 
  18. ↑ Woolley, R.; Epps, E. A.; Penston, M. J.; Pocock, S. B. (1970). "Catalogue of stars within twenty-five parsecs of the Sun". Royal Observatory Annals 5. Bibcode: 1970ROAn....5.....W. 
  19. ↑ "Astronomers Announce First Clear Evidence of a Brown Dwarf". Space Telescope Science Institute news release STScI-1995-48. November 29, 1995. http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/48/. 
  20. ↑ 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. doi:10.1007/978-3-319-01162-2_6. ISBN 978-3-319-01162-2. https://www.springer.com/astronomy/book/978-3-319-01161-5. Retrieved 2017-08-29. 
  21. ↑ Howe, Alex R.; McElwain, Michael W.; Mandell, Avi M. (2022). "GJ 229B: Solving the Puzzle of the First Known T Dwarf with the APOLLO Retrieval Code". The Astrophysical Journal 935 (2): 107. doi:10.3847/1538-4357/ac5590. Bibcode: 2022ApJ...935..107H. 
  22. ↑ J. Kelly Beatty; Carolyn Collins Petersen; Andrew Chaikin (1999). The New Solar System. Cambridge University Press. 
  23. ↑ 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. doi:10.1051/0004-6361:20078229. Bibcode: 2008A&A...480..193G. 
  24. ↑ Oppenheimer, B. R.; Kulkarni, S. R.; Matthews, K.; Nakajima, T. (1995-12-01). "Infrared Spectrum of the Cool Brown Dwarf Gl 229B". Science 270 (5241): 1478–1479. doi:10.1126/science.270.5241.1478. ISSN 0036-8075. PMID 7491492. Bibcode: 1995Sci...270.1478O. 
  25. ↑ Geballe, T. R.; Kulkarni, S. R.; Woodward, Charles E.; Sloan, G. C. (1996-08-01). "The Near-Infrared Spectrum of the Brown Dwarf Gliese 229B". The Astrophysical Journal 467 (2): L101–L104. doi:10.1086/310203. ISSN 0004-637X. Bibcode: 1996ApJ...467L.101G. 
  26. ↑ Oppenheimer, B. R.; Kulkarni, S. R.; Matthews, K.; van Kerkwijk, M. H. (1998-08-01). "The Spectrum of the Brown Dwarf Gliese 229B". The Astrophysical Journal 502 (2): 932–943. doi:10.1086/305928. ISSN 0004-637X. Bibcode: 1998ApJ...502..932O. 
  27. ↑ Saumon, D.; Geballe, T. R.; Leggett, S. K.; Marley, M. S.; Freedman, R. S.; Lodders, K.; Fegley, ((B., Jr.)); Sengupta, S. K. (2000-09-01). "Molecular Abundances in the Atmosphere of the T Dwarf GL 229B". The Astrophysical Journal 541 (1): 374–389. doi:10.1086/309410. ISSN 0004-637X. Bibcode: 2000ApJ...541..374S. 
  28. ↑ Schultz, A. B.; Allard, F.; Clampin, M.; McGrath, M.; Bruhweiler, F. C.; Valenti, J. A.; Plait, P.; Hulbert, S. et al. (1998-01-01). "First Results from the Space Telescope Imaging Spectrograph: Optical Spectra of Gliese 229B". The Astrophysical Journal 492 (2): L181–L184. doi:10.1086/311103. ISSN 0004-637X. Bibcode: 1998ApJ...492L.181S. 
  29. ↑ Calamari, Emily; Faherty, Jacqueline K.; Burningham, Ben; Gonzales, Eileen; Bardalez-Gagliuffi, Daniella; Vos, Johanna M.; Gemma, Marina; Whiteford, Niall et al. (2022-12-01). "An Atmospheric Retrieval of the Brown Dwarf Gliese 229B". The Astrophysical Journal 940 (2): 164. doi:10.3847/1538-4357/ac9cc9. ISSN 0004-637X. Bibcode: 2022ApJ...940..164C. 
  30. ↑ Howe, Alex R.; Mandell, Avi M.; McElwain, Michael W. (June 2023). "Investigating Possible Binarity for GJ 229B". The Astrophysical Journal Letters 951 (2): L25. doi:10.3847/2041-8213/acdd76. Bibcode: 2023ApJ...951L..25H. 
  31. ↑ Kawashima, Yui; Kawahara, Hajime; Kasagi, Yui; Ishikawa, Hiroyuki Tako; Masuda, Kento; Kotani, Takayuki; Kudo, Tamoyuki; Hirano, Teruyuki et al. (2025). "Atmospheric Retrieval of Subaru/IRD High-resolution Spectrum of the Archetype T-type Brown Dwarf Gl 229 B". The Astrophysical Journal 988 (1): 53. doi:10.3847/1538-4357/adddbd. Bibcode: 2025ApJ...988...53K. 
  32. ↑ Tuomi, Mikko et al. (2014). "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 441 (2): 1545. doi:10.1093/mnras/stu358. Bibcode: 2014MNRAS.441.1545T. 
  33. ↑ Feng, Fabo; Butler, R. Paul; Shectman, Stephen A.; Crane, Jeffrey D.; Vogt, Steve; Chambers, John; Jones, Hugh R. A.; Wang, Sharon Xuesong et al. (2020). "Search for Nearby Earth Analogs. II. Detection of Five New Planets, Eight Planet Candidates, and Confirmation of Three Planets around Nine Nearby M Dwarfs". The Astrophysical Journal Supplement Series 246 (1): 11. doi:10.3847/1538-4365/ab5e7c. Bibcode: 2020ApJS..246...11F. 



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Categories: [Binary stars] [Flare stars] [Gliese and GJ objects] [Lepus (constellation)] [M-type main-sequence stars] [Henry Draper Catalogue objects] [Durchmusterung objects] [Hipparcos objects]

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