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Gliese 229

Coordinates: Sky map 06h 10m 34.6154s, −21° 51′ 52.715″
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Gliese 229

Gliese 229 A and B
Observation data
Epoch J2000      Equinox J2000
Constellation Lepus
Right ascension 06h 10m 34.61494s[1]
Declination −21° 51′ 52.6564″[1]
Apparent magnitude (V) 8.14
Characteristics
Evolutionary stage Main sequence / Brown dwarf
Spectral type M1Ve [2]+T7+T8[3]
U−B color index +1.222[2]
B−V color index +1.478[2]
Variable type Flare star
Astrometry
Radial velocity (Rv)4.23±0.12[1] km/s
Proper motion (μ) RA: −135.692(11) mas/yr[1]
Dec.: −719.178(17) mas/yr[1]
Parallax (π)173.5740 ± 0.0170 mas[1]
Distance18.791 ± 0.002 ly
(5.7612 ± 0.0006 pc)
Absolute magnitude (MV)9.326[4]
Absolute bolometric
magnitude (Mbol)		7.96[5]
Orbit[4][6]
CompanionGliese 229 B
Period (P)216.925+10.604
−10.352 yr
Semi-major axis (a)28.933+1.008
−1.000 AU
Eccentricity (e)0.853±0.002
Inclination (i)5.497+0.153
−0.162°
Longitude of the node (Ω)145.946+0.306
−0.294°
Periastron epoch (T)2466912+97
−63
Argument of periastron (ω)
(secondary)		358.285+0.836
−0.846°
Semi-amplitude (K1)
(primary)		0.081674+0.001688
−0.001680 km/s
Details
A
Mass0.579[4] M☉
Radius0.69[7] R☉
Luminosity (bolometric)0.0430[4] L☉
Luminosity (visual, LV)0.0158[nb 1] L☉
Temperature3,700[5] K
Rotation27.3±0.2 d[8]
Rotational velocity (v sin i)1[9] km/s
Ba+Bb
MassBa: 38.1±1.0[3] MJ
Bb: 34.4±1.5[3] MJup
Radius1.105±0.025[10] RJup
Luminosity (bolometric)Ba: 10-5.41 ± 0.04[3] L☉
Bb: 10-5.58 ± 0.04[3] L☉
Surface gravity (log g)Ba: 5.11 ± 0.01[3] dex
Bb: 5.03±0.01[3] cgs
TemperatureBa: 860 ± 20[3] K
Bb: 770 ± 20[3] K
Age2.45 ± 0.20[3] Gyr
Other designations
NSV 2863, BD−21°1377, GJ 229, HD 42581, HIP 29295, SAO 171334, LHS 1827, TYC 5945-765-1
Database references
SIMBADA
B
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

Gliese 229 (also written as Gl 229 or GJ 229) is a multiple system composed of a red dwarf and two brown dwarfs[3], located 18.8 light years away in the constellation Lepus. The primary component has 58% of the mass of the Sun,[4] 69% of the Sun's radius,[7] and a very low projected rotation velocity of 1 km/s at the stellar equator.[9]

A light curve for Gliese 229 showing a small flare, adapted from Byrne et al. (1985)[2]

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.[11] 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.[12] The orbit of this star through the Milky Way galaxy has an eccentricity of 0.07 and an orbital inclination of 0.005.[2]

Companions

[edit]

Brown dwarf

[edit]

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,[13][14] It was the first brown dwarf to be confirmed. 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),[6][10] 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.[15] This object has a surface temperature of 950 K.[16]

Gliese 229B is the prototype of the T-dwarfs, due to the detection of methane in its spectrum.[17] It also shows other molecules in its atmosphere, namely water vapor,[18] carbon monoxide[19] and probably ammonia.[20] Atomic absorption lines of caesium,[21] sodium and potassium are also detected.[22]

The most recent parameters for Gliese 229 B as of 2022 come from a combination of data from radial velocity, astrometry, and imaging, showing that it is about 60.4 times the mass of Jupiter, and on an eccentric orbit with a semi-major axis of about 28.9 AU and an orbital period of about 217 years.[6]

Inconsistencies between the measured mass and luminosity of Gliese 229 B suggested that it may in fact be an unresolved binary brown dwarf.[4][23] Further evidence that Gliese 229B is an equal-mass binary comes from high-resolution spectroscopy from the Subaru Telescope.[24] The binary was resolved in 2024 with VLT/GRAVITY and VLT/CRIRES+. The components are called Gliese 229 Ba (38.1±1.0 MJ) and Gliese 229 Bb (34.4±1.5 MJ). The pair is a tight binary 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.[3] Additional radial velocity changes between two epochs were detected in Gliese 229B with Keck NIRSPEC. This team independently discovered the binarity of Gliese 229B.[25]

Planetary system

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In March 2014, a super-Neptune mass planet candidate was announced in a much closer-in orbit around GJ 229.[26] 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 an unconfirmed candidate, the study estimated a significantly lower minimum mass for it.[27] As of 2022, most sources consider both planets to be confirmed.[6][28][29][30]

The Gliese 229 A planetary system[27]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
c ≥7.268±1.256 M🜨 0.339±0.011 121.995±0.161 0.19±0.08 — —
b ≥8.478±2.033 M🜨 0.898±0.031 526.115±4.300 0.10±0.06 — —

If the planets Gliese 229 Ab & c orbit in the same plane as the brown dwarf Gliese 229 B, their true masses would be significantly greater than their minimum masses, making them both nearly as massive as Saturn.[nb 2]

See also

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References

[edit]
  1. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d e f 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. Bibcode:1985MNRAS.214..119B. doi:10.1093/mnras/214.2.119.
  3. ^ a b c d e f g h i j k l Xuan, Jerry W.; Mérand, A.; Thompson, W.; Zhang, Y.; Lacour, S.; Blakely, D.; Mawet, D.; Oppenheimer, R.; Kammerer, J.; Batygin, K.; Sanghi, A.; Wang, J.; Ruffio, J.-B.; Liu, M. C.; Knutson, H. (2024-10-16). "The cool brown dwarf Gliese 229 B is a close binary". Nature: 1–5. arXiv:2410.11953. doi:10.1038/s41586-024-08064-x. ISSN 1476-4687.
  4. ^ a b c d e f Brandt, G. Mirek; Dupuy, Trent J.; Li, Yiting; Chen, Minghan; Brandt, Timothy D.; Wong, Tin Long Sunny; Currie, Thayne; Bowler, Brendan P.; Liu, Michael C.; Best, William M. J.; Phillips, Mark W. (2021). "Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3". The Astronomical Journal. 162 (6): 301. arXiv:2109.07525. Bibcode:2021AJ....162..301B. doi:10.3847/1538-3881/ac273e. S2CID 237532125.
  5. ^ a b 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. S2CID 16238033. Data from CDS table J/A+A/478/507 Archived 2016-10-06 at the Wayback Machine.
  6. ^ a b c d Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.
  7. ^ a b 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.
  8. ^ Díez Alonso, E.; Caballero, J. A.; Montes, D.; De Cos Juez, F. J.; Dreizler, S.; Dubois, F.; Jeffers, S. V.; Lalitha, S.; Naves, R.; Reiners, A.; Ribas, I.; Vanaverbeke, S.; Amado, P. J.; Béjar, V. J. S.; Cortés-Contreras, M.; Herrero, E.; Hidalgo, D.; Kürster, M.; Logie, L.; Quirrenbach, A.; Rau, S.; Seifert, W.; Schöfer, P.; Tal-Or, L. (2019). "CARMENES input catalogue of M dwarfs. IV. New rotation periods from photometric time series". Astronomy and Astrophysics. 621: A126. arXiv:1810.03338. Bibcode:2019A&A...621A.126D. doi:10.1051/0004-6361/201833316. S2CID 111386691.
  9. ^ a b 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. arXiv:astro-ph/0702634. Bibcode:2007A&A...467..259R. doi:10.1051/0004-6361:20066991. S2CID 8672566.
  10. ^ a b 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. arXiv:2203.11706. Bibcode:2022ApJ...935..107H. doi:10.3847/1538-4357/ac5590. S2CID 247597251.
  11. ^ 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. Bibcode:1995ApJ...450..392S. doi:10.1086/176149.
  12. ^ Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg. 22: 1. Bibcode:1969VeARI..22....1G.
  13. ^ "Astronomers Announce First Clear Evidence of a Brown Dwarf". Space Telescope Science Institute news release STScI-1995-48. November 29, 1995. Archived from the original on 9 July 2008. Retrieved 24 September 2013.
  14. ^ 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 (ed.), 50 Years of Brown Dwarfs - From Prediction to Discovery to Forefront of Research, Astrophysics and Space Science Library, vol. 401, Springer, pp. 81–111, arXiv:1404.4430, doi:10.1007/978-3-319-01162-2_6, ISBN 978-3-319-01162-2, S2CID 118304613, archived from the original on 2015-02-19, retrieved 2017-08-29
  15. ^ J. Kelly Beatty; Carolyn Collins Petersen; Andrew Chaikin (1999). The New Solar System. Cambridge University Press.
  16. ^ 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. S2CID 9331798.
  17. ^ 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. Bibcode:1995Sci...270.1478O. doi:10.1126/science.270.5241.1478. ISSN 0036-8075. PMID 7491492.
  18. ^ 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. arXiv:astro-ph/9606056. Bibcode:1996ApJ...467L.101G. doi:10.1086/310203. ISSN 0004-637X.
  19. ^ 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. arXiv:astro-ph/9802299. Bibcode:1998ApJ...502..932O. doi:10.1086/305928. ISSN 0004-637X.
  20. ^ 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. arXiv:astro-ph/0003353. Bibcode:2000ApJ...541..374S. doi:10.1086/309410. ISSN 0004-637X.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  21. ^ Schultz, A. B.; Allard, F.; Clampin, M.; McGrath, M.; Bruhweiler, F. C.; Valenti, J. A.; Plait, P.; Hulbert, S.; Baum, S.; Woodgate, B. E.; Bowers, C. W.; Kimble, R. A.; Maran, S. P.; Moos, H. W.; Roesler, F. (1998-01-01). "First Results from the Space Telescope Imaging Spectrograph: Optical Spectra of Gliese 229B". The Astrophysical Journal. 492 (2): L181–L184. Bibcode:1998ApJ...492L.181S. doi:10.1086/311103. ISSN 0004-637X.
  22. ^ Calamari, Emily; Faherty, Jacqueline K.; Burningham, Ben; Gonzales, Eileen; Bardalez-Gagliuffi, Daniella; Vos, Johanna M.; Gemma, Marina; Whiteford, Niall; Gaarn, Josefine (2022-12-01). "An Atmospheric Retrieval of the Brown Dwarf Gliese 229B". The Astrophysical Journal. 940 (2): 164. arXiv:2210.13614. Bibcode:2022ApJ...940..164C. doi:10.3847/1538-4357/ac9cc9. ISSN 0004-637X.
  23. ^ Howe, Alex R.; Mandell, Avi M.; McElwain, Michael W. (June 2023). "Investigating Possible Binarity for GJ 229B". The Astrophysical Journal Letters. 951 (2): L25. arXiv:2306.08450. Bibcode:2023ApJ...951L..25H. doi:10.3847/2041-8213/acdd76.
  24. ^ Kawashima, Yui; Kawahara, Hajime; Kasagi, Yui; Ishikawa, Hiroyuki Tako; Masuda, Kento; Kotani, Takayuki; Kudo, Tamoyuki; Hirano, Teruyuki; Kuzuhara, Masayuki (2024-10-15). "Atmospheric retrieval of Subaru/IRD high-resolution spectrum of the archetype T-type brown dwarf Gl 229 B". arXiv:2410.11561 [astro-ph].
  25. ^ 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". The Astrophysical Journal Letters. 974 (2): L30. arXiv:2410.11999. doi:10.3847/2041-8213/ad7714. ISSN 2041-8205.
  26. ^ 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. arXiv:1403.0430. Bibcode:2014MNRAS.441.1545T. doi:10.1093/mnras/stu358. S2CID 32965505.
  27. ^ a b Feng, Fabo; Butler, R. Paul; Shectman, Stephen A.; Crane, Jeffrey D.; Vogt, Steve; Chambers, John; Jones, Hugh R. A.; Wang, Sharon Xuesong; Teske, Johanna K.; Burt, Jenn; Díaz, Matías R.; Thompson, Ian B. (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. arXiv:2001.02577. Bibcode:2020ApJS..246...11F. doi:10.3847/1538-4365/ab5e7c. S2CID 210064560.
  28. ^ "Planet GJ 229 A b". Extrasolar Planets Encyclopaedia. 1995. Retrieved 7 September 2022.
  29. ^ "GJ 229". NASA Exoplanet Archive. Archived from the original on 4 December 2023. Retrieved 7 September 2022.
  30. ^ Reylé, Céline; Jardine, Kevin; Fouqué, Pascal; Caballero, Jose A.; Smart, Richard L.; Sozzetti, Alessandro (30 April 2021). "The 10 parsec sample in the Gaia era". Astronomy & Astrophysics. 650: A201. arXiv:2104.14972. Bibcode:2021A&A...650A.201R. doi:10.1051/0004-6361/202140985. S2CID 233476431. Data available at https://gruze.org/10pc/ Archived 2023-03-12 at the Wayback Machine

Notes

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  1. ^ Using the absolute visual magnitude of Gliese 229 A and the absolute visual magnitude of the Sun , the visual luminosity can be calculated by
  2. ^ 7.268 ME/sin(5.497°) = 75.87 ME
    8.478 ME/sin(5.497°) = 88.50 ME
[edit]
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