Alpha Octantis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Octans |
| Right ascension | 21h 04m 43.06347s |
| Declination | −77° 01′ 25.5735″ |
| Apparent magnitude (V) | 5.13 |
| Characteristics | |
| Spectral type | F4III + F5III (spectroscopic binary) |
| U−B color index | +0.13 |
| B−V color index | +0.490±0.008 |
| Variable type | EB |
| Astrometry | |
| Radial velocity (Rv) | 85.9±1.5 km/s |
| Proper motion (μ) | RA: +22.5215 mas/yr Dec.: −369.325 mas/yr |
| Parallax (π) | 22.5215±0.0955 mas |
| Distance | 144.8 ± 0.6 ly (44.4 ± 0.2 pc) |
| Absolute magnitude (MV) | 1.93±0.02 |
| Orbit | |
| Period (P) | 9.073 d |
| Eccentricity (e) | 0.39 |
| Periastron epoch (T) | 2,435,302.404 |
| Argument of periastron (ω) (secondary) | 276° |
| Semi-amplitude (K1) (primary) | 47 km/s |
| Semi-amplitude (K2) (secondary) | 47 km/s |
| Details | |
| Mass | 1.42 M☉ |
| Radius | 3.69 R☉ |
| Temperature | 6,270 K |
| Metallicity [Fe/H] | 0.07 dex |
| Rotational velocity (v sin i) | 85 km/s |
| Age | 1.5±0.1 Gyr |
| Other designations | |
| α Oct, CD−77°1053, CPD−77°1474, FK5 787, GC 29343, HD 199532, HIP 104043, HR 8021, SAO 257879, PPM 374864, LTT 8327, NLTT 50332 | |
| Database references | |
| SIMBAD | data |
Alpha Octantis is a binary star system in the constellation of Octans. The name is Latinized from α Octantis. Despite being labeled the "alpha" star by Lacaille, it is not the brightest star in the constellation—that title belongs to Nu Octantis. It is visible to the naked eye as a faint, yellow-white-hued point of light with an overall apparent visual magnitude of approximately 5.13. The system is located approximately 148 light-years away from the Sun based on parallax.
This is a double-lined spectroscopic binary star which consists of two similar giant stars, each with spectral type F, orbiting each other with a period of just over 9 days and an eccentricity of 0.39. The pair form a Beta Lyrae-type eclipsing binary system, dropping by magnitude 0.04 during the primary eclipse. This system is a bright X-ray source with a luminosity of 22.78×1029 ergs s−1. The system displays an infrared excess suggesting the presence of a debris disk; with a temperature of 219 K and is orbiting at a distance of 9.8 AU from its host star.