Groombridge 34

Groombridge 34 is a binary star system in the northern constellation of Andromeda. It was listed as entry number 34 in A Catalogue of Circumpolar Stars, published posthumously in 1838 by British astronomer Stephen Groombridge.[10] Based upon parallax measurements taken by the Gaia spacecraft, the system is located about 11.6 light-years (3.6 parsecs) from the Sun. This positions the pair among the nearest stars to the Solar System.

Groombridge 34
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Groombridge 34 A
Right ascension 00h 18m 22.8850s[1]
Declination +44° 01′ 22.6373″[1]
Apparent magnitude (V) 8.119[2]
Groombridge 34 B
Right ascension 00h 18m 25.8244s[3]
Declination +44° 01′ 38.0912″[3]
Apparent magnitude (V) 11.007[2]
Characteristics
Spectral type M1.4V + M4.1V[2]
U−B color index +1.24/+1.40[4]
B−V color index +1.56/+1.80[4]
Variable type Flare stars
Astrometry
Groombridge 34 A
Radial velocity (Rv)+11.62±0.08[5] km/s
Proper motion (μ) RA: 2891.525±0.061[1] mas/yr
Dec.: 411.903±0.034[1] mas/yr
Parallax (π)280.6902 ± 0.0429[1] mas
Distance11.620 ± 0.002 ly
(3.5626 ± 0.0005 pc)
Groombridge 34 B
Proper motion (μ) RA: 2863.284±0.069[3] mas/yr
Dec.: 336.529±0.039[3] mas/yr
Parallax (π)280.7866 ± 0.0519[3] mas
Distance11.616 ± 0.002 ly
(3.5614 ± 0.0007 pc)
Orbit[6]
CompanionGroombridge 34 B
Period (P)2,600 yr
Semi-major axis (a)41.15″
Eccentricity (e)0.00
Inclination (i)61.4°
Longitude of the node (Ω)45.3°
Periastron epoch (T)1745
Details
Groombridge 34 A
Mass0.38±0.05[7] M☉
Radius0.38±0.05[7] R☉
Luminosity~0.022[7] L☉
Habitable zone inner limit0.112[8] AU
Habitable zone outer limit0.239[8] AU
Surface gravity (log g)4.87±0.04[7] cgs
Temperature3607±68[7] K
Metallicity [Fe/H]−0.34±0.09[7] dex
Rotation43.86±0.56 days[7]
Rotational velocity (v sin i)1.09±0.79[7] km/s
Age~3.02[2] Gyr
Groombridge 34 B
Mass0.15±0.02[7] M☉
Radius0.18±0.03[7] R☉
Luminosity~8.5×10−4[7] L☉
Habitable zone inner limit0.048[8] AU
Habitable zone outer limit0.103[8] AU
Surface gravity (log g)5.08±0.15[7] cgs
Temperature3304±70[7] K
Metallicity [Fe/H]−0.37±0.10[2] dex
Age~2.754[2] Gyr
Other designations
GX/GQ Andromedae, BD+43° 44, GCTP 49, GJ 15 A/B, G 171-047/171-048, HD 1326, HIP 1475, LHS 3/4, LTT 10108/10109, SAO 36248.[9]
Database references
SIMBADGJ 15 A
GJ 15 Ab
GJ 15 B
ARICNSGJ 15 A
GJ 15 B

Both components are small, dim red dwarf stars that are too faint to be seen with the naked eye. They orbit around their common barycenter in a nearly circular orbit with a separation of about 147 AU and a period of around 2,600 years.[6] Both stars exhibit random variation in luminosity due to flares and they have been given variable star designations: the brighter member Groombridge 34 A is designated GX And, while the smaller component is designated GQ And.[11]

The star system has a relatively high proper motion of 2.9 arc seconds per year,[12] and is moving away from the Solar System at a velocity of 11.6 km/s.[5] It achieved perihelion some 15,000 years ago when it came within 11 ly (3.5 pc) of the Sun.[12]

GX Andromedae

The most massive and luminous component of the pair has the variable star designation GX Andromedae. It is a main-sequence red dwarf star of spectral type M1.4[2] that varies his brightness due to stellar flares. Gaia observations suggest a rotation period of 44 days and a magnetic activity cycle of roughly 9 years.[13]

GQ Andromedae

The smaller companion bears the variable star name GQ Andromedae. It is a red dwarf main sequence star that undergoes flare events like the primary; it has a spectral type M4.1,[2] so it has also a lower effective temperature.

Planetary system

In August 2014, a planet orbiting around Groombridge 34 A was reported.[14] The planet's existence was deduced from analysis of the radial velocities of the parent star by the Eta-Earth Survey using HIRES at Keck Observatory. At the time of its discovery, it was the sixth-nearest-known exoplanet.

Using the CARMENES spectrograph combined with the measurements of the HARPS and HIRES spectrographs, researchers failed to detect the purported Groombridge 34 Ab. However, they did propose another that another planet (Groombridge 34 Ac, GJ 15 Ac) could be orbiting the parent star.[15]

This discrepancy was later reconciled with new HIRES observations, covering a longer span of time, where both planets were recovered, constraining their minimum mass to 3.03 M⊕ for Groombridge 34 Ab and 36 M⊕ for Groombridge Ac. Their orbital periods are 11.4 and approximately 7,600 days, respectively. To date, this is the fifth-closest multi-planet system to our Sun, hosting the longest-period Neptune-mass exoplanet discovered so far.[7]

The Groombridge 34 A planetary system[7]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
Ab ≥ 3.03+0.46
−0.44 M⊕		 0.072+0.003
−0.004		 11.4407+0.0017
−0.0016		 0.094+0.091
−0.065		 — —
Ac ≥ 36+25
−18 M⊕		 5.4+1.0
−0.9		 ~7,600 0.27+0.28
−0.19		 — —

See also

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Mann, Andrew W.; et al. (May 2015), "How to Constrain Your M Dwarf: Measuring Effective Temperature, Bolometric Luminosity, Mass, and Radius", The Astrophysical Journal, 804 (1): 38, arXiv:1501.01635, Bibcode:2015ApJ...804...64M, doi:10.1088/0004-637X/804/1/64, S2CID 19269312, 64.
  3. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  4. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode:1986EgUBV........0M.
  5. Nidever, David L.; et al. (August 2002), "Radial Velocities for 889 Late-Type Stars", The Astrophysical Journal Supplement Series, 141 (2): 503–522, arXiv:astro-ph/0112477, Bibcode:2002ApJS..141..503N, doi:10.1086/340570, S2CID 51814894.
  6. Lippincott, S. L. (March 1972), "Parallax and orbital motion of the two nearby long period visual binaries Groombridge 34 and ADS 9090.", Astronomical Journal, 77: 165–168, Bibcode:1972AJ.....77..165L, doi:10.1086/111261.
  7. Pinamonti, M.; Damasso, M.; Marzari, F.; Sozzetti, A.; Desidera, S.; Maldonado, J.; Scandariato, G.; Affer, L.; Lanza, A. F.; Bignamini, A.; Bonomo, A. S.; Borsa, F.; Claudi, R.; Cosentino, R.; Giacobbe, P.; González-Álvarez, E.; González Hernández, J. I.; Gratton, R.; Leto, G.; Malavolta, L.; Martinez Fiorenzano, A.; Micela, G.; Molinari, E.; Pagano, I.; Pedani, M.; Perger, M.; Piotto, G.; Rebolo, R.; Ribas, I.; et al. (2018). "The HADES RV Programme with HARPS-N at TNG. VIII. GJ15A: A multiple wide planetary system sculpted by binary interaction". Astronomy and Astrophysics. 617: A104. arXiv:1804.03476. Bibcode:2018A&A...617A.104P. doi:10.1051/0004-6361/201732535. S2CID 54990041.
  8. Cantrell, Justin R.; et al. (October 2013), "The Solar Neighborhood XXIX: The Habitable Real Estate of Our Nearest Stellar Neighbors", The Astronomical Journal, 146 (4): 99, arXiv:1307.7038, Bibcode:2013AJ....146...99C, doi:10.1088/0004-6256/146/4/99, S2CID 44208180.
  9. "V* GX And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-02-09.
  10. Groombridge, Stephen (1838), Airy, George Biddell (ed.), A Catalogue of Circumpolar Stars, J. Murray, p. 2.
  11. Petit, M. (October 1990), "Catalogue des étoiles variables ou suspectes dans le voisinage du Soleil", Astronomy and Astrophysics Supplement (in French), 85 (2): 971, Bibcode:1990A&AS...85..971P.
  12. Bailer-Jones, C. A. L. (March 2015). "Close encounters of the stellar kind". Astronomy & Astrophysics. 575: 13. arXiv:1412.3648. Bibcode:2015A&A...575A..35B. doi:10.1051/0004-6361/201425221. S2CID 59039482. A35.
  13. Morris, Brett M.; Agol, Eric; Davenport, James R. A.; Hawley, Suzanne L. (2018). "Spotting stellar activity cycles in Gaia astrometry". Monthly Notices of the Royal Astronomical Society. 476 (4): 5408. arXiv:1802.09943. Bibcode:2018MNRAS.476.5408M. doi:10.1093/mnras/sty568. S2CID 73564680.
  14. Howard, Andrew W.; et al. (October 2014), "The NASA-UC-UH ETA-Earth Program. IV. A Low-mass Planet Orbiting an M Dwarf 3.6 PC from Earth", The Astrophysical Journal, 794 (1): 9, arXiv:1408.5645, Bibcode:2014ApJ...794...51H, doi:10.1088/0004-637X/794/1/51, S2CID 17361592, 51.
  15. Trifonov, T; Kürster, M; Zechmeister, M; Tal-Or, L; Caballero, J; Quirrenbach, A; Ribas, I; Reiners, A (2018). "The CARMENES search for exoplanets around M dwarfs. First visual-channel radial-velocity measurements and orbital parameter updates of seven M-dwarf planetary systems". Astronomy & Astrophysics. 609: A117. arXiv:1710.01595. Bibcode:2018A&A...609A.117T. doi:10.1051/0004-6361/201731442. S2CID 119340839.
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