Xi Octantis

Xi Octantis, Latinized from ξ Octantis, is a solitary^[17] variable star in the southern circumpolar constellation Octans. It has an apparent magnitude of about 5.3, allowing it to be faintly seen with the naked eye; however, this varies slightly. Located 514 light years away, the object is receding with a heliocentric radial velocity of 22 km/s.

A light curve for Xi Octantis, plotted from TESS data^[18]

ξ Octantis

Location of ξ Octantis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	22h 50m 22.8139s[1]
Declination	−80° 07′ 25.842″[1]
Apparent magnitude (V)	5.32 - 5.36[2]
Characteristics
Evolutionary stage	main sequence[3]
Spectral type	B6 V[4] (B5/7 V)[5]
U−B color index	−0.48[6][7]
B−V color index	−0.13[6]
Variable type	SPB[8]
Astrometry
Radial velocity (Rv)	22.1±0.5[9] km/s
Proper motion (μ)	RA: +20.003 mas/yr[1] Dec.: −12.607 mas/yr[1]
Parallax (π)	6.35±0.0644 mas[1]
Distance	514 ± 5 ly (157 ± 2 pc)
Absolute magnitude (MV)	−0.57[10]
Details
Mass	4.02±0.05[3] M☉
Radius	3.0±0.5[11] R☉
Luminosity	360+24 −22[3] L☉
Surface gravity (log g)	4.09[11] cgs
Temperature	14,050[12] K
Metallicity [Fe/H]	−0.1[12] dex
Rotational velocity (v sin i)	30[13] km/s
Age	46+25 −16[14] Myr
Other designations
ξ Oct, 77 G. Octantis, CD−80°828, CPD−80°1055, GC 31821, HD 215573, HIP 112781, HR 8663, SAO 258946[15][16]
Database references
SIMBAD	data

Xi Octantis has a stellar classification of B6 V,^[4] indicating that it is an ordinary B-type main-sequence star. Hintler et al. gives it a luminosity class IV (subgiant)^[19] while Houk and Cowley gives a classification intermediate between a B5 and B7 dwarf.^[5] Nevertheless, it has 4 times the mass of the Sun^[3] and is 3 times larger.^[11] It shines with a luminosity of 360 L_☉^[3] from its photosphere at an effective temperature of 14,050 K,^[12] giving it a whitish blue glow. Xi Octantis is 46 million years old^[14] – 64.8% through its short main sequence lifetime^[12] – and spins modestly with a projected rotational velocity of 30 km/s.^[13]

When the Hipparcos catalogue was released in 1997, Xi Octantis was found to vary in magnitude^[20] — ranging from 5.32 to 5.36 based on data from the International Variable Star Index.^[2] It has since been classified as a Slowly pulsating B-dwarf with a period of 1.78 days.^[2]