Theta Antliae
Binary star system in the constellation Antlia
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Theta Antliae is a binary star system in the southern constellation of Antlia. Its identifier is a Bayer designation that was Latinized from θ Antliae, and is abbreviated Tet Ant or θ Ant, respectively. The pair have a combined apparent visual magnitude of +4.78,[3] which is bright enough to be faintly visible to the naked eye. 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 340 light-years (104 parsecs) from Earth. The system is receding with a heliocentric radial velocity of +24 km/s.[5]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Antlia[1] |
| Right ascension | 09h 44m 12.09512s[2] |
| Declination | −27° 46′ 10.1011″[2] |
| Apparent magnitude (V) | 4.79[3] |
| Characteristics | |
| Spectral type | G7 III + A8 Vm[4] |
| U−B color index | +0.35[3] |
| B−V color index | +0.50[3] |
| Astrometry | |
| Radial velocity (Rv) | +24.0[5] km/s |
| Proper motion (μ) | RA: −53.23[2] mas/yr Dec.: +37.24[2] mas/yr |
| Parallax (π) | 9.61±0.46 mas[2] |
| Distance | 340 ± 20 ly (104 ± 5 pc) |
| Absolute magnitude (MV) | −0.30[1] |
| Orbit[6] | |
| Period (P) | 18.423±0.019 yr |
| Semi-major axis (a) | 0.10904±0.00032″ |
| Eccentricity (e) | 0.4956±0.0031 |
| Inclination (i) | 126.19±0.44° |
| Longitude of the node (Ω) | 175.66±0.44° |
| Periastron epoch (T) | 2020.913±0.025 |
| Argument of periastron (ω) (secondary) | 138.04±0.86° |
| Details[7] | |
| θ Ant A | |
| Mass | 1.8±0.1 M☉ |
| θ Ant B | |
| Mass | 2.1±0.5 M☉ |
| Other designations | |
| θ Antliae, Tet Ant, θ Ant, CD−27 6881, FK5 366, HD 84367, HIP 47758, HR 3871, SAO 177908, PPM 256646[8] | |
| Database references | |
| SIMBAD | data |
The binary nature of this system was discovered by W. S. Finsen in 1952.[7] The primary component of this system, θ Antliae A, has a stellar classification of A8 Vm,[4] 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.[4] The pair have an orbital period of 18.423 years, a significant eccentricity of 0.4956, and an angular semi-major axis of 0.10904 arcseconds.[6]