Omega Octantis

Omega Octantis, (latinized from ω Octantis), is a solitary,^[14] bluish-white hued star located in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.87,^[2] allowing it to be faintly seen with the naked eye. Based on the object's parallax measurements, it is estimated to be 328 light years distant.^[1] However, it is drifting closer with a heliocentric radial velocity −7.6 km/s.^[6]

ω Octantis

Location of ω Oct (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	15h 11m 08.79214s[1]
Declination	−84° 47′ 16.0295″[1]
Apparent magnitude (V)	5.87±0.01[2]
Characteristics
Evolutionary stage	main sequence[3]
Spectral type	B9.5 V[4]
U−B color index	−0.13[5]
B−V color index	−0.06[5]
Astrometry
Radial velocity (Rv)	−7.6±3[6] km/s
Proper motion (μ)	RA: +2.984 mas/yr[1] Dec.: −9.385 mas/yr[1]
Parallax (π)	9.9406 ± 0.0591 mas[1]
Distance	328 ± 2 ly (100.6 ± 0.6 pc)
Absolute magnitude (MV)	+0.94[7]
Details
Mass	2.54[3] M☉
Radius	2.35±0.06[8] R☉
Luminosity	50.5+2.5 −2.4[3] L☉
Surface gravity (log g)	4.21[9] cgs
Temperature	10,759±366[9] K
Metallicity [Fe/H]	0.00[10] dex
Rotational velocity (v sin i)	36[11] km/s
Age	197[9] Myr
Other designations
ω Oct, 23 G. Octantis[12], CPD−84°490, GC 20223, HD 131596, HIP 74296, HR 5557, SAO 258717[13]
Database references
SIMBAD	data

Omega Octantis has a stellar classification of B9.5 V,^[4] indicating that it is a main-sequence star between the B9 and A0 classes. Helmut A. Abt & Nidia I. Morrell gave a slightly updated class of B9.5 Vs,^[15] which includes sharp (narrow) absorption lines in Omega Octantis' spectrum due to slow rotation. It has a mass 2.54 times that of the Sun^[3] and is calculated to be 197 million years old,^[9] having completed 40% of its main sequence lifetime.^[3] It has a luminosity of 50.5 L_☉,^[3] which comes from a radius of 2.35 R_☉ and an effective temperature of 10,759 K. In 2012, George A. Gontcharov calculated a solar metallicity for Omega Octantis,^[10] and it is spinning modestly with a projected rotational velocity of 36 km/s.^[11] The slow rotation is consistent with the spectral classification from Abt & Morell (1995).^[15]

References

1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. 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.
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. 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°. Bibcode:1975mcts.book.....H.
5. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
6. 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. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
7. 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. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
8. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881.
9. David, Trevor J.; Hillenbrand, Lynne A. (12 May 2015). "The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. eISSN 1538-4357.
10. Gontcharov, G. A. (December 2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters. 38 (12): 771–782. arXiv:1606.08814. Bibcode:2012AstL...38..771G. doi:10.1134/S1063773712120031. ISSN 0320-0108. S2CID 118345778.
11. 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.
12. 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.
13. "Omega Oct". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 21, 2022.
14. 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.
15. Abt, Helmut A.; Morrell, Nidia I. (July 1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". The Astrophysical Journal Supplement Series. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182. ISSN 0067-0049.