Alpha Octantis

Alpha Octantis is a binary star^[12] 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.^[3] The system is located approximately 148 light-years away from the Sun based on parallax.

Alpha Octantis

A light curve for Alpha Octantis plotted from TESS data[1]
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	21h 04m 43.06347s[2]
Declination	−77° 01′ 25.5735″[2]
Apparent magnitude (V)	5.13[3]
Characteristics
Spectral type	F4III + F5III (spectroscopic binary)[4]
U−B color index	+0.13[5]
B−V color index	+0.490±0.008[3]
Variable type	EB[6]
Astrometry
Radial velocity (Rv)	85.9±1.5[3] km/s
Proper motion (μ)	RA: +22.5215[2] mas/yr Dec.: −369.325[2] mas/yr
Parallax (π)	22.5215±0.0955 mas[2]
Distance	144.8 ± 0.6 ly (44.4 ± 0.2 pc)
Absolute magnitude (MV)	1.93±0.02[7]
Orbit[4]
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[8] M☉
Radius	3.69[9] R☉
Temperature	6,270[7] K
Metallicity [Fe/H]	0.07[7] dex
Rotational velocity (v sin i)	85[10] km/s
Age	1.5±0.1[7] 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[11]
Database references
SIMBAD	data

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.^[4] The pair form a Beta Lyrae-type eclipsing binary system, dropping by magnitude 0.04 during the primary eclipse.^[6] This system is a bright X-ray source with a luminosity of 22.78×10²⁹ ergs s⁻¹.^[13] 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.^[14]