Xi Octantis

ξ Octantis

Location of ξ Octantis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	22^h 50^m 22.8139^s[1]
Declination	−80° 07′ 25.8418″[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, 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]

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]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
2. Watson, C. L.; Henden, A. A.; Price, A. (May 2006). "The International Variable Star Index (VSX)". Society for Astronomical Sciences Annual Symposium. 25: 47. Bibcode:2006SASS...25...47W.
3. Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy and Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. ISSN 0004-6361. S2CID 55586789.
4. Cucchiaro, A.; Macau-Hercot, D.; Jaschek, M.; Jaschek, C. (October 1977). "Spectral classification from the ultraviolet line features of S2/68 spectra. II. Late B-type stars". Astronomy and Astrophysics Supplement Series. 30: 71–79. Bibcode:1977A&AS...30...71C. ISSN 0365-0138.
5. Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations -90_ to -53_ƒ0. Bibcode:1975mcts.book.....H.
6. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 – L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
7. Reed, B. Cameron (May 2003). "Catalog of Galactic OB Stars". The Astronomical Journal. 125 (5): 2531–2533. Bibcode:2003AJ....125.2531R. doi:10.1086/374771. eISSN 1538-3881. ISSN 0004-6256.
8. Samus’, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (January 2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. ISSN 1063-7729. S2CID 255195566.
9. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. ISSN 1063-7737. S2CID 119231169.
10. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 255204555.
11. De Cat, P.; Aerts, C. (October 2002). "A study of bright southern slowly pulsating B stars". Astronomy & Astrophysics. 393 (3): 965–981. Bibcode:2002A&A...393..965D. doi:10.1051/0004-6361:20021068. eISSN 1432-0746. ISSN 0004-6361.
12. Smith, K. C.; Dworetsky, M. M. (July 1993). "Elemental abundances in normal late-B and HgMn stars from co-added IUE spectra. I. Iron-peak elements". Astronomy and Astrophysics. 274: 335–355. Bibcode:1993A&A...274..335S. ISSN 0004-6361.
13. Levato, H.; Grosso, M. (June 2004). "New Projected Rotational Velocities of All Southern B-type Stars of the Bright Star Catalogue". Astronomical Society of the Pacific. 215: 51. Bibcode:2004IAUS..215...51L.
14. Grosbol, P. J. (June 1978). "Space velocities and ages of nearby early-type stars". Astronomy and Astrophysics Supplement Series. 32: 409–421. Bibcode:1978A&AS...32..409G. ISSN 0365-0138.
15. "ksi Oct". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 9 June 2022.
16. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
17. Eggleton, P. P.; Tokovinin, A. A. (11 September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. eISSN 1365-2966. ISSN 0035-8711.
18. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 24 September 2022.
19. Hiltner, W. A.; Garrison, R. F.; Schild, R. E. (July 1969). "MK Spectral Types for Bright Southern OB Stars". The Astrophysical Journal. 157: 313. Bibcode:1969ApJ...157..313H. doi:10.1086/150069. eISSN 1538-4357. ISSN 0004-637X.
20. Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; Hoeg, E.; Bastian, U.; Bernacca, P. L.; Crézé, M.; Donati, F.; Grenon, M.; Grewing, M.; Leeuwen, van; Marel, van der; Mignard, F.; Murray, C. A.; Poole, Le; Schrijver, H.; Turon, C.; Arenou, F.; Froeschlé, M.; Petersen, C. S. (July 1997). "The HIPPARCOS Catalogue". Astronomy and Astrophysics. 323: L49 – L52. Bibcode:1997A&A...323L..49P. ISSN 0004-6361.