Gliese 65

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Gliese 65 A/B
Gliese 65 DSS2.png
Gliese 65, as seen during the Digitized Sky Survey
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Cetus
Gliese 65 A (BL Ceti)
Right ascension 01h 39m 01.3773s [1]
Declination –17° 57′ 02.587″ [1]
Apparent magnitude  (V)12.8 [2]
Gliese 65 B (UV Ceti)
Right ascension 01h 39m 01.6377s [3]
Declination –17° 57′ 01.001″ [3]
Apparent magnitude  (V)12.8 [2]
Characteristics
Gliese 65 A (BL Ceti)
Spectral type M5.5V [4]
U−B color index 1.10
B−V color index 1.87
Variable type UV Cet [5]
Gliese 65 B (UV Ceti)
Spectral type M6 V [4]
Variable type UV Cet [6]
Astrometry
Parallax (π)371.92 ± 0.42  mas [7]
Distance 8.770 ± 0.010  ly
(2.689 ± 0.003  pc)
Gliese 65 A (BL Ceti)
Proper motion (μ)RA: 3385.316 [1]   mas/yr
Dec.: 544.386 [1]   mas/yr
Absolute magnitude  (MV)15.7 [2]
Gliese 65 B (UV Ceti)
Proper motion (μ)RA: 3178.694 [3]   mas/yr
Dec.: 584.061 [3]   mas/yr
Absolute magnitude  (MV)15.7 [2]
Orbit [7]
Period (P)26.38±0.002 yr
Semi-major axis (a)2.0584±0.0097 [8] "
(5.459±0.002  AU )
Eccentricity (e)0.6172±0.0001
Inclination (i)128.0±0.1°
Longitude of the node (Ω)325.9±0.1°
Periastron epoch (T)41333±8  MJD
(17 January 1972)
Argument of periastron (ω)
(secondary)		103.2±0.1°
Details
Gliese 65 A
Mass 0.122±0.002 [7]   M☉
Radius 0.165±0.006 [8]   R☉
Luminosity 0.00147±0.00005 [9]   L☉
Surface gravity (log g)5.092±0.015 [8]   cgs
Temperature 2784±58 [9]   K
Metallicity [Fe/H]−0.03±0.20 [8]   dex
Rotation 0.2430±0.0005 [10] days
Rotational velocity (v sin i)28.2±2 [8]  km/s
Gliese 65 B
Mass 0.116±0.002 [7]   M☉
Radius 0.159±0.006 [8]   R☉
Luminosity0.00125±0.00005 [9]   L☉
Surface gravity (log g)5.113±0.015 [8]   cgs
Temperature 2728±60 [9]   K
Metallicity [Fe/H]−0.12±0.20 [8]   dex
Rotation 0.2268±0.0003 [10] days
Rotational velocity (v sin i)30.6±2 [8]  km/s
Other designations
GJ  65, G 272-61, L  726-8, PLX  343.1
Gliese 65 A: BL Ceti, LHS  9, LP  768-27
Gliese 65 B: UV Ceti, LHS  10, LP  768-26
Database references
SIMBAD The system
A (BL Cet)
B (UV Cet)

Gliese 65, also known as Luyten 726-8, is a binary star system that is one of Earth's nearest neighbors, at 8.8 light-years (2.7 parsecs ) from Earth in the constellation Cetus. The two component stars are both flare stars with the variable star designations BL Ceti and UV Ceti.

Contents

Star system

UV Ceti by Andrew Posa (1982) Toronto Andrew Posa 01.jpg
UV Ceti by Andrew Posa (1982)

The star system was discovered in 1948 by Willem Jacob Luyten in the course of compiling a catalog of stars of high proper motion; he noted its exceptionally high proper motion of 3.37 arc seconds annually and cataloged it as Luyten 726-8. [11] The two stars are of nearly equal brightness, with visual magnitudes of 12.7 and 13.2 as seen from Earth. They orbit one another every 26.5 years. The distance between the two stars varies from 2.1 to 8.8 astronomical units (310 to 1,320  Gm ). The Gliese 65 system is approximately 2.63 parsecs (8.58  ly ) from Earth's Solar System, in the constellation Cetus, and is thus the seventh-closest star system to Earth. Its own nearest neighbor is Tau Ceti, 0.98 pc (3.20 ly) away from it. If km/s then approximately 28,700 years ago Gliese 65 was at its minimal distance of 2.21 pc (7.2 ly) from the Sun. [12]

Gliese 65 A was later found to be a variable star and given the variable star designation BL Ceti. [5] It is a red dwarf of spectral type M5.5V. It is also a flare star, and classified as a UV Ceti variable type, but it is not nearly as remarkable or extreme in its behavior as its companion star UV Ceti.

An ultraviolet light curve for UV Ceti, adapted from Beskin et al. (2017). The main plot shows the full flare event and the inset plot shows the time around peak brightness with an expanded time scale. UVCetLightCurve.png
An ultraviolet light curve for UV Ceti, adapted from Beskin et al. (2017). The main plot shows the full flare event and the inset plot shows the time around peak brightness with an expanded time scale.

Soon after the discovery of Gliese 65 A, the companion star Gliese 65 B was discovered. Like Gliese 65 A, this star was also found to be variable and given the variable star designation UV Ceti. [6] Although UV Ceti was not the first flare star discovered, it is the most prominent example of such a star, so similar flare stars are now classified as UV Ceti type variable stars. This star goes through fairly extreme changes of brightness: for instance, in 1952, its brightness increased by 75 times in only 20 seconds. UV Ceti is a red dwarf of spectral type M6V. [4]

Both stars are listed as spectral standard stars for their respective classes, being considered typical examples of the classes. [4]

In approximately 31,500 years, Gliese 65 will have a close encounter with Epsilon Eridani at the minimal distance of about 0.93 ly. Gliese 65 can penetrate a conjectured Oort cloud about Epsilon Eridani, which may gravitationally perturb some long-period comets. The duration of mutual transit of two star systems within 1 ly from each other is about 4,600 years. [14]

Gliese 65 is a possible member of the Hyades Stream. [15]

Candidate planet

In 2024, a candidate super-Neptune-mass planet was detected in the Gliese 65 system via astrometry with Very Large Telescope's GRAVITY instrument. If it exists, it would orbit one of the two stars (it is unclear which) with a period of 156 days. [7] The planet's properties change slightly depending on which star it orbits, but in general its mass is estimated to be about 40 ME and the semi-major axis is about 30% of an astronomical unit. It is estimated to be about seven times the size of Earth based on mass-radius relationships. [7]

The Gliese 65 planetary system [7] [nb 1]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b(unconfirmed)39±7  M🜨
36±6 M🜨 		0.283±0.002
0.274±0.002		156±10.33±0.30
0.27±0.21		88±6 °
89±9 ° 		~7 (estimate)  R🜨

Notes

  1. ↑ The parameters are slightly different depending on whether the planet orbits star A (above) or star B (below).

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    References

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    2. 1 2 3 4 Houdebine, Éric R.; Mullan, D. J.; Doyle, J. G.; de la Vieuville, Geoffroy; Butler, C. J.; Paletou, F. (2019). "The Mass-Activity Relationships in M and K Dwarfs. I. Stellar Parameters of Our Sample of M and K Dwarfs". The Astronomical Journal. 158 (2): 56. arXiv: 1905.07921 . Bibcode:2019AJ....158...56H. doi: 10.3847/1538-3881/ab23fe . S2CID   159041104.
    3. 1 2 3 4 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.
    4. 1 2 3 4 Kirkpatrick, J. Davy; Henry, Todd J.; McCarthy, Donald W. Jr. (1991). "A standard stellar spectral sequence in the red/near-infrared - Classes K5 to M9". Astrophysical Journal Supplement. 77: 417. Bibcode:1991ApJS...77..417K. doi: 10.1086/191611 .
    5. 1 2 "Query= BL Cet". General Catalogue of Variable Stars . Centre de Données astronomiques de Strasbourg. Archived from the original on 2016-03-03. Retrieved 2009-12-16.
    6. 1 2 "Query= UV Cet". General Catalogue of Variable Stars . Centre de Données astronomiques de Strasbourg. Archived from the original on 2016-03-03. Retrieved 2009-12-16.
    7. 1 2 3 4 5 6 7 Abuter, R.; et al. (GRAVITY Collaboration) (May 2024). "Astrometric detection of a Neptune-mass candidate planet in the nearest M-dwarf binary system GJ65 with VLTI/GRAVITY". Astronomy & Astrophysics . 685: L9. arXiv: 2404.08746 . Bibcode:2024A&A...685L...9G. doi:10.1051/0004-6361/202449547.
    8. 1 2 3 4 5 6 7 8 9 Kervella, Pierre; et al. (October 2016), "The red dwarf pair GJ65 AB: inflated, spinning twins of Proxima. Fundamental parameters from PIONIER, NACO, and UVES observations", Astronomy & Astrophysics, 593, arXiv: 1607.04351 , Bibcode:2016A&A...593A.127K, doi:10.1051/0004-6361/201628631
    9. 1 2 3 4 MacDonald, James; et al. (June 2018), "The Magnetic Binary GJ 65: A Test of Magnetic Diffusivity Effects", The Astrophysical Journal, 860 (1): 15, arXiv: 1711.09434 , Bibcode:2018ApJ...860...15M, doi: 10.3847/1538-4357/aac2c0
    10. 1 2 Barnes, J. R.; et al. (October 2017), "Surprisingly different star-spot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB", Monthly Notices of the Royal Astronomical Society, 471 (1): 811–823, arXiv: 1706.03979 , Bibcode:2017MNRAS.471..811B, doi: 10.1093/mnras/stx1482
    11. ↑ Luyten, W. J. (December 1949). "New stars with proper motions exceeding 0.5" annually". The Astronomical Journal . 55: 15. Bibcode:1949AJ.....55...15L. doi: 10.1086/106322 .
    12. ↑ "Annotations on V* UV Cet object". Centre de Données astronomiques de Strasbourg. Archived from the original on 2014-11-23. Retrieved 2010-04-14.
    13. ↑ Beskin, G.; Karpov, S.; Plokhotnichenko, V.; Stepanov, A.; Tsap, Yu. (January 2017). "Discovery of the subsecond linearly polarized spikes of synchrotron origin in the UV Ceti giant optical flare". Publications of the Astronomical Society of Australia. 34. arXiv: 1702.06660 . Bibcode:2017PASA...34...10B. doi: 10.1017/pasa.2017.3 . S2CID   125084280.
    14. ↑ Potemine, Igor Yu. (April 2010). "Transit of Luyten 726-8 within 1 ly from Epsilon Eridani". arXiv: 1004.1557 [astro-ph.SR].
    15. ↑ Montes, D.; et al. (2001). "Late-type members of young stellar kinematic groups - I. Single stars". MNRAS. 328 (1): 45–63. arXiv: astro-ph/0106537 . Bibcode:2001MNRAS.328...45M. doi: 10.1046/j.1365-8711.2001.04781.x . S2CID   55727428.

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