Theta Antliae

Theta Antliae (θ Ant, θ Antliae) is the Bayer designation for a binary star in the southern constellation of Antlia. The pair have a combined apparent visual magnitude of +4.78;[2] the brighter component is magnitude +5.30 while the secondary is +6.18.[9] Based upon parallax measurements, it is located at a distance of around 430 light-years (130 parsecs) from Earth.

θ Antliae
Location of θ Antliae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Antlia
Right ascension 09h 44m 12.09512s[1]
Declination –27° 46′ 10.1011″[1]
Apparent magnitude (V) 4.79[2]
Characteristics
Spectral type A8 Vm + G7 III[3]
U−B color index +0.35[2]
B−V color index +0.50[2]
Astrometry
Radial velocity (Rv)+24.0[4] km/s
Proper motion (μ) RA: –53.23[1] mas/yr
Dec.: +37.24[1] mas/yr
Parallax (π)7.5602 ± 0.8169[5] mas
Distanceapprox. 430 ly
(approx. 130 pc)
Orbit[6]
Companionθ Ant B
Period (P)18.32 yr
Semi-major axis (a)0.134″
Eccentricity (e)0.445
Inclination (i)124°
Longitude of the node (Ω)176.8°
Periastron epoch (T)1965.75
Details[7]
θ Ant A
Mass1.8 ± 0.1 M☉
θ Ant B
Mass2.1 ± 0.5 M☉
Other designations
CD–27 6881, HIP 47758, FK5 366, HD 84367, HR 3871, SAO 177908.[8]
Database references
SIMBADdata

The primary component of this system, θ Antliae A, has a stellar classification of A8 Vm,[3] indicating that it is an A-type main sequence star with enhanced metallic lines in its spectrum. The companion, θ Antliae B, is a giant star with a classification of G7 III.[3] The pair have an orbital period of 18.3 years, a significant eccentricity of 0.445, and they have an angular separation of 0.1 arcseconds.[6]

References
  1. van Leeuwen, F. (November 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, S2CID 18759600.
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  3. Ginestet, N.; Carquillat, J. M. (December 2002), "Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components", The Astrophysical Journal Supplement Series, 143 (2): 513–537, Bibcode:2002ApJS..143..513G, doi:10.1086/342942.
  4. Wilson, Ralph Elmer (1953), "General catalogue of stellar radial velocities", Washington, Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  5. 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.
  6. Heintz, W. D. (March 1982), "Orbits of 16 visual binaries", Astronomy and Astrophysics Supplement Series, 47: 569–573, Bibcode:1982A&AS...47..569H.
  7. Docobo, J. A.; Andrade, M. (2012). "Dynamical and physical properties of 22 binaries discovered by W. S. Finsen". Monthly Notices of the Royal Astronomical Society. 428 (1): 321–339. Bibcode:2013MNRAS.428..321D. doi:10.1093/mnras/sts045.
  8. "tet Ant". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-28.
  9. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
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