Groombridge 34

Groombridge 34

Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	00^h 18^m 22.88532^s[1]
Declination	+44° 01′ 22.6282″[1]
Apparent magnitude (V)	8.119/11.007[2]
Characteristics
Spectral type	M1.4V + M4.1V[2]
U−B color index	+1.24/+1.40[3]
B−V color index	+1.56/+1.80[3]
Variable type	Flare stars
Astrometry
Radial velocity (Rv)	+11.62±0.08[4] km/s
Proper motion (μ)	RA: +2888.92 ± 0.60[1] mas/yr Dec.: +410.10 ± 0.48[1] mas/yr
Parallax (π)	278.76 ± 0.77[1] mas
Distance	11.70 ± 0.03 ly (3.587 ± 0.010 pc)
Orbit[5]
Companion	Groombridge 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
GX And
Mass	0.404[6] M☉
Radius	0.3863 ± 0.0021[7] R☉
Luminosity (bolometric)	0.02589[note 1] L☉
Luminosity (visual, LV)	0.00637[note 2] L☉
Habitable zone inner limit	0.112[8] AU
Habitable zone outer limit	0.239[8] AU
Surface gravity (log g)	4.89[6] cgs
Temperature	3,730 ± 49[6] K
Metallicity [Fe/H]	-0.32 dex
GQ And
Mass	0.159[2] M☉
Radius	0.192[2] R☉
Luminosity (bolometric)	~0.00262[note 1] L☉
Luminosity (visual, LV)	0.00041[note 2] L☉
Habitable zone inner limit	0.048[8] AU
Habitable zone outer limit	0.103[8] AU
Temperature	3,218[2] K
Metallicity [Fe/H]	−0.30[2] dex
Other designations
GX/GQ Andromedae, BD+43° 44, GCTP 49, GJ 15 A/B, Gl 171-047/171-048, HD 1326, HIP 1475, LHS 3/4, LTT 10108/10109, LFT 31/32, SAO 36248, Vys 085 A/B.[9]

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 Hipparcos spacecraft, the system is located about 11.7 light-years from the Sun. This positions the pair among the nearest stars to the Solar System.

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.^[5] 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.^[4] It achieved perihelion some 15,000 years ago when it came within 11 ly (3.5 pc) of the Sun.^[12]

Planetary system

In August 2014, a planet orbiting around Groombridge 34 A was reported.^[7] 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.

The planet is thought to have a minimum mass of 5.35 ± 0.75 Earth masses,^[13] and at its discovery was the sixth nearest known exoplanet.

The Groombridge 34 A planetary system

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥ 5.35±0.75 M⊕	0.0717±0.0034	11.4433±0.0017	0.12?	—	—

See also

• Groombridge 34 in fiction
• List of nearest stars

Notes

1. From $\begin{smallmatrix}L=4 \pi R^2 \sigma T_{\rm eff}^4 \end{smallmatrix}$, where $\begin{smallmatrix}L \end{smallmatrix}$ is the luminosity, $\begin{smallmatrix}R \end{smallmatrix}$ is the radius, $\begin{smallmatrix}T_{\rm eff}\end{smallmatrix}$ is the effective surface temperature and $\begin{smallmatrix}\sigma \end{smallmatrix}$ is the Stefan–Boltzmann constant
2. Using the absolute visual magnitude of Gliese 15 A, $\scriptstyle M_{V_{\ast}}=10.32$, and Gliese 15 B, $\scriptstyle M_{V_{\ast}}=13.29$, with the absolute visual magnitude of the Sun, $\scriptstyle M_{V_{\odot}}=4.83$, the two visual luminosities of the stars can be calculated by $\scriptstyle \frac{L_{V_{\ast}}}{L_{V_{\odot}}}=10^{0.4\left(M_{V_{\odot}} - M_{V_{\ast}}\right)}$

References

1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
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, 64.
3. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data. SIMBAD, Bibcode:1986EgUBV........0M.
4. 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.
5. 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.
6. Berger, D. H.; et al. (2006). "First Results from the CHARA Array. IV. The Interferometric Radii of Low-Mass Stars". The Astrophysical Journal 644 (1): 475–483. arXiv:astro-ph/0602105. Bibcode:2006ApJ...644..475B. doi:10.1086/503318.
7. 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, 51.
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.
9. "V* GX And -- Flare Star", SIMBAD Astronomical Database (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. A35.
13. Howard, Andrew; et al., "The NASA-UC-UH Eta-Earth Program: IV. A Low-mass Planet Orbiting an M Dwarf 3.6 PC from Earth", Astrophysics Earth and Planetary Astrophysics, arXiv:1408.5645, Bibcode:2014ApJ...794...51H, doi:10.1088/0004-637X/794/1/51.

External links

• SolStation entry
• www.richweb.f9.co.uk/
• Image Groombridge 34
• The One Hundred Nearest Star Systems, RECONS