Xi Octantis
Slowly pulsating B-dwarf in Octans
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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.
  | |
| 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]