| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Antlia[2] |
| Right ascension | 09h 32m 18.38648s[3] |
| Declination | −28° 37′ 39.9685″[3] |
| Apparent magnitude (V) | 6.27 to 6.83[4] |
| Characteristics | |
| Spectral type | A9V |
| B−Vcolor index | 0.33 |
| Variable type | Eclipsing binaryW UMa type |
| Astrometry | |
| Proper motion (μ) | RA: −89.375mas/yr[3] Dec.: +44.049mas/yr[3] |
| Parallax (π) | 12.6116±0.0203 mas[3] |
| Distance | 258.6 ± 0.4 ly (79.3 ± 0.1 pc) |
| Absolute magnitude (MV) | 1.963[5] (2.25 + 3.42)[6] |
| Orbit[7] | |
| Period (P) | 0.59145447(30) days |
| Semi-major axis (a) | 3.82±0.02 R☉ |
| Inclination (i) | 74.02±0.14° |
| Semi-amplitude (K1) (primary) | 75±1 km/s |
| Semi-amplitude (K2) (secondary) | 234±1 km/s |
| Details[6] | |
| A | |
| Mass | 1.66±0.10 M☉ |
| Radius | 2.09±0.11 R☉ |
| Luminosity | 10.0±2.2 L☉ |
| Surface gravity (log g) | 4.02±0.03 cgs |
| Temperature | 7,100±200 K |
| B | |
| Mass | 0.55±0.05 M☉ |
| Radius | 1.31±0.06 R☉ |
| Luminosity | 3.4±0.7 L☉ |
| Temperature | 6,859±200 K |
| Age | 1.9[7] Gyr |
| Other designations | |
| CD-28°7373,HD 82610,SAO 177619,HIP 46810,HR 3798. | |
| Database references | |
| SIMBAD | data |
S Antliae is aW Ursae Majoris-typeeclipsing binary star inAntlia.
S Antiliae is classed as an A-type W Ursae Majoris variable, since the primary is hotter than the secondary and the drop in magnitude is caused by the latter passing in front of the former. S Antiliae varies in apparent magnitude from 6.27 to 6.83 over a period of 15.6 hours.[4] The system shines with a combined spectrum of A9V.[citation needed]
The system's orbital period is about 0.591 days. The stars' centres are an average of 3.82 times the Sun's radius apart. The system will evolve into anAlgol variable.[6]
Calculating the properties of the component stars indicates that the primary star has a mass 1.66 times and a diameter 2.09 times that of the Sun, and the secondary has a mass 0.55 times and a diameter 1.31 times that of the Sun. The primary has asurface temperature of 7,100 K, while the secondary is a little cooler at 6,859 K.[6] The two stars have similarluminosity andspectral type as they have acommon envelope and share stellar material.[citation needed] The system is thought to be around two billion years old.[7]
Based upon an annualparallax shift of 12.6116 milliarc seconds as measured by theGaia satellite,[3] this system is 259light-years (79.3parsecs) fromEarth. Analysing and recalibrating yields a parallax of 13.30 and hence a distance of 250light-years (76parsecs).[5]
The star's variability was first recorded in 1888 by H.M. Paul,[8] when it had the shortest known period of any variable star. It was initially thought to be anAlgol-type eclipsing binary, but this was discounted byE.C. Pickering on account of it lacking a shallow minimum in its maximum and the width of its minimum period.Alfred H. Joy noted the similarity of its light curve toW Ursae Majoris in 1926, concluding the system was indeed an eclipsing binary with two stars of spectral type A8.[9]
