# Astronomy:41 G. Arae

Short description
Multiple star in the constellation Ara
41 G. Arae
Observation data
Equinox J2000.0]] (ICRS)
Constellation Ara
Right ascension  17h 19m 03.83574s[1]
Declination −46° 38′ 10.4467″[1]
5.48[2] (5.61 / 8.88)[3]
Characteristics
Spectral type G8V + M0V[4]
U−B color index +0.38[5]
B−V color index +0.80[6]
R−I color index +0.41[6]
Astrometry
Radial velocity (Rv)25.3 ± 0.1[7] km/s
Proper motion (μ) RA: 1037.56[1] mas/yr
Dec.: 108.99[1] mas/yr
Parallax (π)113.61 ± 0.69[1] mas
Distance28.7 ± 0.2 ly
(8.80 ± 0.05 pc)
Absolute magnitude (MV)5.74[8]
Orbit[3]
Companion41 G. Ara B
Period (P)953 yr
Semi-major axis (a)13.341″
Eccentricity (e)0.825
Inclination (i)40.5°
Longitude of the node (Ω)137.3°
Periastron epoch (T)1907.5
Argument of periastron (ω)
(secondary)
329.7°
Details
41 G. Ara A
Mass0.810[9] M
Surface gravity (log g)4.5[6] cgs
Temperature5,305[6] K
Metallicity [Fe/H]−0.35[6] dex
Rotational velocity (v sin i)4.5[10] km/s
Age5.5–6.3[11] Gyr
41 G. Ara B
Mass0.52[4] M
Other designations
41 G. Arae, CD-46° 11370, GJ 666, HD 156274, HIP 84720, HR 6416, LHS 444, LTT 6886, SAO 227816, LPM 636, LFT 1334.
Database references
41 G. Ara A
41 G. Ara B
ARICNS41 G. Ara A
41 G. Ara B

41 G. Arae (abbreviated to 41 G. Ara), also known as GJ 666, is a trinary star system in the constellation Ara. Although often called just 41 Arae, it is more accurate to call it 41 G. Arae, as the number 41 is the Gould designation (Flamsteed only covered the northern hemisphere).

The primary star in this system is a G-type main sequence star with a stellar classification of G8V. It has about 81% of the mass of the Sun, and 79% of the Sun's radius.[9] The fainter member of the pair, a red dwarf,[4] has a peculiar spectrum that shows a deficiency in elements with a higher atomic number than Helium. No planetary companions have been detected in orbit around these stars.[12]

The two stars share a highly elliptical orbit that takes several centuries to complete. The estimates of the period range from 693 to 2,200 years,[13] and the average separation of the two stars is about 210 AUs (or 210 times the average distance between the Earth and the Sun).

41 G. Arae is most likely a triple, comprising the following components: Gliese 666A supposed as a spectroscopic binary, and Gliese 666B as its companion. Two other visual companions were proposed, but neither share the system's motion.[14]

This system has a relatively high proper motion, moving over a second of arc across the sky each year. The space velocity components of this system are [U, V, W] = [+38, +30, −19] km/s.[6] The stars in this system show low chromospheric activity, and have a net space velocity of 52 km/s relative to the Sun. This, in combination with their low metallicity, shows that the pair belongs to the old disk population.[6]

## References

1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode2007A&A...474..653V
2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues 2237. Bibcode2002yCat.2237....0D.
3. "Entry 171903.85-463810.1", Sixth Catalog of Orbits of Visual Binary Stars (United States Naval Observatory), retrieved 2016-06-07.
4. Zakhozhaj, V. A. (1979). "Nearest stars". Vestnik Khar'kovskogo Universiteta (SIMBAD) 190: 52–77. Bibcode1979VKha..190...52Z.
5. Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory 4: 99. Bibcode1966CoLPL...4...99J.
6. Perrin, M.-N.; de Strobel, G. Cayrel; Dennefeld, M. (1988), "High S/N detailed spectral analysis of four G and K dwarfs within 10 PC of the sun", Astronomy and Astrophysics 191 (2): 237–247, Bibcode1988A&A...191..237P
7. Nordström, B. et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics 418 (3): 989–1019, doi:10.1051/0004-6361:20035959, Bibcode2004A&A...418..989N
8. Holmberg, J. et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics 501 (3): 941–947, doi:10.1051/0004-6361/200811191, Bibcode2009A&A...501..941H.
9. Takeda, G. et al. (February 2007), "Structure and Evolution of Nearby Stars with Planets II. Physical Properties of ~ 1000 Cool Stars from the SPOCS Catalog", The Astrophysical Journal Supplement Series 168 (2): 297–318, doi:10.1086/509763, Bibcode2007ApJS..168..297T
10. Schröder, C.; Reiners, A.; Schmitt, J. H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics 493 (3): 1099–1107, doi:10.1051/0004-6361:200810377, Bibcode2009A&A...493.1099S
11. Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal 687 (2): 1264–1293, doi:10.1086/591785, Bibcode2008ApJ...687.1264M
12. Santos, N. C. et al. (July 2005), "Spectroscopic metallicities for planet-host stars: Extending the samples", Astronomy and Astrophysics 437 (3): 1127–1133, doi:10.1051/0004-6361:20052895, Bibcode2005A&A...437.1127S
13. de Mello, G. F. Porto; del Peloso, E. F.; Ghezzi, L. (2006), "Astrobiologically interesting stars within 10 parsecs of the Sun", Astrobiology 6 (2): 308–331, doi:10.1089/ast.2006.6.308, PMID 16689649, Bibcode2006AsBio...6..308P
14. Jenkins, J. S.; Díaz, M.; Jones, H. R. A.; Butler, R. P.; Tinney, C. G.; O'Toole, S. J.; Carter, B. D.; Wittenmyer, R. A. et al. (2015). "The observed distribution of spectroscopic binaries from the Anglo-Australian Planet Search". Monthly Notices of the Royal Astronomical Society 453 (2): 1439. doi:10.1093/mnras/stv1596. Bibcode2015MNRAS.453.1439J.