Astronomy:Zeta Trianguli Australis

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Short description: Binary star system in the constellation Triangulum Australe
Zeta Trianguli Australis
Location of ζ Trianguli Australis (circled in red)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Triangulum Australe
Right ascension  16h 28m 28.14362s[1]
Declination −70° 05′ 03.8419″[1]
Apparent magnitude (V) 4.91[2]
Characteristics
Spectral type F9V + M4V[2][3]
U−B color index +0.02[4]
B−V color index +0.55[5]
Astrometry
Radial velocity (Rv)+8.3[6] km/s
Proper motion (μ) RA: 200.742[7] mas/yr
Dec.: 109.341[7] mas/yr
Parallax (π)82.8699 ± 0.1627[7] mas
Distance39.36 ± 0.08 ly
(12.07 ± 0.02 pc)
Absolute magnitude (MV)4.49[8]
Orbit[9]
Period (P)12.97662±0.00017 d
Eccentricity (e)0.01442±0.00021
Inclination (i)35±19[10]°
Periastron epoch (T)JD 2452752.31955
Argument of periastron (ω)
(secondary)		252.98°±0.80°
Semi-amplitude (K1)
(primary)		7.4988±0.0016 km/s
Details
ζ TrA A
Mass1.12[11] M☉
Radius1.02±0.02[12] R☉
Luminosity1.41+0.15
−0.09[12] L☉
Surface gravity (log g)4.42+0.04
−0.05[12] cgs
Temperature6,210+180
−120[12] K
Metallicity [Fe/H]−0.09±0.06[13] dex
Rotation13 days[5]
Rotational velocity (v sin i)3.23[14] km/s
Age600–900[15] Myr
ζ TrA B
Mass0.30[10] M☉
Temperature3,327[10] K
Other designations
CPD−69°2558, FK5 610, GJ 624, HD 147584, HIP 80686, HR 6098, SAO 253554, LTT 6558[16]
Database references
SIMBADdata
ARICNSdata

Zeta Trianguli Australis is a spectroscopic binary star system in the southern constellation Triangulum Australe. The pair have a combined apparent visual magnitude of 4.90,[4] which is bright enough to be visible to the naked eye. Based on parallax measurements, the system is located at a distance of approximately 39.4 light years from Earth.[7] After closing to within 31.3 ly (9.59 pc) some 436,600 years ago,[17] it is now drifting farther away with a radial velocity of +8.3 km/s.[6]

The pair orbit each other once every 13 days, and the orbital eccentricity is a low 0.014, making their orbit nearly circular.[9] The primary component has a stellar classification of F9V, matching an F-type main-sequence star. It has a mass equal to 1.12 times the mass of the Sun,[11] a radius 1.06 times the radius of the Sun, and irradiated at an effective temperature of 6,032 K, slightly hotter than the Sun as well.[13] The companion is a small red dwarf star with a class in the range of M1–7V[2] and 40% of the Sun's mass.[11] The age of the system is estimated at 600–900 million years.[15]

Any objects orbiting the pair in a circumbinary orbit should have an orbital separation of 0.217 AU or higher; otherwise its orbit would be unstable due to gravitational interactions.[12]

Somewhat surprisingly for a star located at a declination of 70° S, it is a candidate swarm member of the Ursa Major moving group.[18] However, there is some evidence to the contrary.[5]

References

  1. ↑ 1.0 1.1 van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V.  Note: see VizieR catalogue I/311.
  2. ↑ 2.0 2.1 2.2 Ammler-von Eiff, M. et al. (June 2016), "Coronagraphic search for wide substellar companions among members of the Ursa Major moving group", Astronomy & Astrophysics 591: id. A84, doi:10.1051/0004-6361/201526625, Bibcode: 2016A&A...591A..84A. 
  3. ↑ Gray, R. O. et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal 132 (1): 161–170, doi:10.1086/504637, Bibcode: 2006AJ....132..161G. 
  4. ↑ 4.0 4.1 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. ↑ 5.0 5.1 5.2 Maldonado, J. et al. (October 2010), "A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups", Astronomy and Astrophysics 521: A12, doi:10.1051/0004-6361/201014948, Bibcode: 2010A&A...521A..12M. 
  6. ↑ 6.0 6.1 Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  7. ↑ 7.0 7.1 7.2 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  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, Bibcode: 2009A&A...501..941H. 
  9. ↑ 9.0 9.1 Skuljan, Jovan (2004), "Accurate orbital parameters for the bright southern spectroscopic binary ζ Trianguli Australis – an interesting case of a near-circular orbit", Monthly Notices of the Royal Astronomical Society 352 (3): 975, doi:10.1111/j.1365-2966.2004.07988.x, Bibcode: 2004MNRAS.352..975S. 
  10. ↑ 10.0 10.1 10.2 Pérez-Couto, X.; Docobo, J. Á.; Campo, P. P. (2024-01-29). "Methodology for obtaining the relative orbit and individual masses of Gaia astrometric binaries" (in en). Astronomy & Astrophysics 682: A12. doi:10.1051/0004-6361/202348125. ISSN 0004-6361. Bibcode: 2024A&A...682A..12P. 
  11. ↑ 11.0 11.1 11.2 Tokovinin, Andrei (April 2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal 147 (4): 14, doi:10.1088/0004-6256/147/4/87, 87, Bibcode: 2014AJ....147...87T. 
  12. ↑ 12.0 12.1 12.2 12.3 12.4 Barbato, D.; Ségransan, D.; Udry, S.; Unger, N.; Bouchy, F.; Lovis, C.; Mayor, M.; Pepe, F. et al. (2023-06-01), "The CORALIE survey for southern extrasolar planets - XIX. Brown dwarfs and stellar companions unveiled by radial velocity and astrometry" (in en), Astronomy & Astrophysics 674: A114, doi:10.1051/0004-6361/202345874, ISSN 0004-6361, Bibcode: 2023A&A...674A.114B.  Zeta TrA's database entry at VizieR.
  13. ↑ 13.0 13.1 Fuhrmann, K.; Chini, R.; Kaderhandt, L.; Chen, Z. (2017-02-10), "Multiplicity among Solar-type Stars", The Astrophysical Journal 836 (1): 139, doi:10.3847/1538-4357/836/1/139, ISSN 0004-637X, Bibcode: 2017ApJ...836..139F. 
  14. ↑ Martínez-Arnáiz, R. et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter", Astronomy and Astrophysics 520: A79, doi:10.1051/0004-6361/200913725, Bibcode: 2010A&A...520A..79M. 
  15. ↑ 15.0 15.1 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, Bibcode: 2008ApJ...687.1264M. 
  16. ↑ "zet TrA". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=zet+TrA. 
  17. ↑ Bailer-Jones, C.A.L. et al. (2018), "New stellar encounters discovered in the second Gaia data release", Astronomy & Astrophysics 616: A37, doi:10.1051/0004-6361/201833456, Bibcode: 2018A&A...616A..37B. 
  18. ↑ Croswell, Ken (2005), "Descendants of the Dipper", Astronomy 33 (3): 40–45, ISSN 0091-6358, Bibcode: 2005Ast....33c..40C, http://www.kencroswell.com/DescendantsOfTheDipper.html. 



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