Lambda Octantis

λ Octantis, Latinized as Lambda Octantis, is a binary star[3] system in the southern circumpolar constellation of Octans.[10] It is visible to the naked eye as a dim point of light with a combined apparent visual magnitude of 5.27.[2] The distance to this system is approximately 398–409 light years, based on parallax, but it is moving closer with a radial velocity of −10 km/s.[7]

Lambda Octantis
Location of λ Octantis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Octans
Right ascension 21h 50m 54.56355s[1]
Declination −82° 43′ 08.0450″[1]
Apparent magnitude (V) 5.27[2] (5.64 + 7.25)[3]
Characteristics
Spectral type G8-K0III[4] + kA3hA7VmA8[5]
U−B color index +0.47[6]/+2.20[5]
B−V color index +0.75[6]
Astrometry
A
Radial velocity (Rv)−10.18±0.13[7] km/s
Proper motion (μ) RA: +69.803[7] mas/yr
Dec.: −33.013[7] mas/yr
Parallax (π)8.1897 ± 0.0878[7] mas
Distance398 ± 4 ly
(122 ± 1 pc)
Absolute magnitude (MV)+0.40[5]
B
Proper motion (μ) RA: +69.025[8] mas/yr
Dec.: −25.496[8] mas/yr
Parallax (π)7.9685 ± 0.0570[8] mas
Distance409 ± 3 ly
(125.5 ± 0.9 pc)
Absolute magnitude (MV)+2.20[5]
Details
A
Radius13.23+0.41
−0.50[7] R☉
Luminosity102.4±1.3[7] L☉
Temperature5,048+98
−76[7] K
Rotational velocity (v sin i)1.8[9] km/s
Age200[5] Myr
Other designations
λ Oct, CPD−83°722, GC 30472, HD 206240, HIP 107843, HR 8280, SAO 258914, CCDM J21509-8243, WDS J21509-8243[10]
Database references
SIMBADdata

The primary, designated component A, is an aging, yellow-hued star with a stellar classification of class G8-K0III[11] and a visual magnitude of 5.64.[3] Having exhausted the supply of hydrogen at its core, it has expanded and cooled off the main sequence, becoming a giant. At present it is about 200[5] million years old and has 13[7] times the girth of the Sun. This star is radiating 102[7] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 5,048 K.[7]

The magnitude 7.25[3] secondary companion, component B, is an Am star with a class of kA3hA7VmA8.[5] This notation indicates it has the calcium K line of an A3 class star, the hydrogen lines of a cooler A7 main sequence star, and the metal lines of an A8 star. As of 2008, it lies at an angular separation of 3.233″ from the primary.[3]

References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644. Vizier catalog entry
  3. Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976. Vizier catalog entry
  4. Houk, Nancy; Cowley, A. P. (1979). Michigan catalogue of two-dimensional spectral types for the HD stars. 1. Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan. Bibcode:1978mcts.book.....H.
  5. Corbally, C. J. (December 1984). "Close visual binaries. III. Parameters and evolutionary status". Astronomical Journal. 89: 1887–1896. Bibcode:1984AJ.....89.1887C. doi:10.1086/113700.
  6. Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers. 42 (2): 443. Bibcode:2014JAVSO..42..443M.Vizier catalog entry
  7. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  8. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  9. De Medeiros, J. R.; et al. (2014). "A catalog of rotational and radial velocities for evolved stars". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. S2CID 54046583. Vizier catalog entry
  10. "lam Oct". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-19.
  11. Hoffleit, D.; Warren, W. H. (1995). "Bright Star Catalogue". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H (5th Revised ed.). 5050. Bibcode:1995yCat.5050....0H.
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