Astronomy:Alpha Octantis

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Short description: Binary star system in the constellation Octans
Alpha Octantis
Location of α Octantis (circled in red)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Octans
Right ascension  21h 04m 43.06347s[1]
Declination −77° 01′ 25.5735″[1]
Apparent magnitude (V) 5.13[2]
Characteristics
Evolutionary stage Main sequence[3]
Spectral type F4III + F5III[4]
U−B color index +0.13[5]
B−V color index +0.490±0.008[2]
Variable type EB[6]
Astrometry
Radial velocity (Rv)85.9±1.5[2] km/s
Proper motion (μ) RA: +22.5215[1] mas/yr
Dec.: −369.325[1] mas/yr
Parallax (π)22.5215 ± 0.0955[1] mas
Distance144.8 ± 0.6 ly
(44.4 ± 0.2 pc)
Absolute magnitude (MV)1.93±0.02[7]
Orbit[4]
Period (P)9.073 d
Eccentricity (e)0.39
Periastron epoch (T)2,435,302.404
Argument of periastron (ω)
(secondary)		276°
Semi-amplitude (K1)
(primary)		47 km/s
Semi-amplitude (K2)
(secondary)		47 km/s
Details
A
Mass1.9[8] M☉
Radius2.0[3] R☉
Luminosity7[3] L☉
Temperature6,700[3] K
Age1.1[8] Gyr
B
Mass2[3] M☉
Radius2.0[3] R☉
Luminosity7[3] L☉
Temperature6,700[3] K
Age1.1[8] Gyr
Other designations
α Oct, CD−77°1053, CPD−77°1474, FK5 787, GC 29343, HD 199532, HIP 104043, HR 8021, SAO 257879, PPM 374864, LTT 8327, NLTT 50332[9]
Database references
SIMBADdata

Alpha Octantis is a binary star[10] system in the constellation of Octans. The name is Latinized from α Octantis. Despite being labeled the "alpha" star by Lacaille, it is not the brightest star in the constellation—that title belongs to Nu Octantis. It is also the faintest "alpha" star overall, with Alpha Mensae a close second.[11] It is visible to the naked eye as a faint, yellow-white-hued point of light with an overall apparent visual magnitude of approximately 5.13.[2] The system is located approximately 148 light-years away from the Sun based on parallax.

A light curve for Alpha Octantis plotted from TESS data[12]

This is a double-lined spectroscopic binary star which consists of two similar main sequence stars, each with spectral type F,[3] orbiting each other with a period of just over 9 days and an eccentricity of 0.39.[4] The pair form a Beta Lyrae-type eclipsing binary system, dropping by magnitude 0.04 during the primary eclipse.[6] This system is a bright X-ray source with a luminosity of 22.78×1029 ergs s−1.[13] The system displays an infrared excess suggesting the presence of a debris disk; with a temperature of 219 K and is orbiting at a distance of 9.8 astronomical unit|AU from its host star.[14]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 "Alpha Octantis". http://stars.astro.illinois.edu/sow/alphaoct.html. 
  4. ↑ 4.0 4.1 4.2 The double-lined binary alpha Octantis, William Buscombe and Pamela M. Morris, The Observatory 80 (February 1960), pp. 28–29, Bibcode: 1960Obs....80...28B.
  5. ↑ HR 8021, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 4, 2008.
  6. ↑ 6.0 6.1 Samus', N. N et al. (2017). "General catalogue of variable stars". Astronomy Reports. 5.1 61 (1): 80. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  7. ↑ Nordström, B. (2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs". Astronomy and Astrophysics 418: 989–1019. doi:10.1051/0004-6361:20035959. Bibcode: 2004A&A...418..989N. 
  8. ↑ 8.0 8.1 8.2 Asensio-Torres, R.; Janson, M.; Bonavita, M.; Desidera, S.; Thalmann, C.; Kuzuhara, M.; Henning, Th; Marzari, F. et al. (2018-11-01). "SPOTS: The Search for Planets Orbiting Two Stars - III. Complete sample and statistical analysis" (in en). Astronomy & Astrophysics 619: A43. doi:10.1051/0004-6361/201833349. ISSN 0004-6361. 
  9. ↑ "* alf Oct". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+alf+Oct. 
  10. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society 389 (2): 869–879. doi:10.1111/j.1365-2966.2008.13596.x. Bibcode: 2008MNRAS.389..869E. 
  11. ↑ Ridpath, Ian. "Star Tales – Octans". http://www.ianridpath.com/startales/octans.html. 
  12. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  13. ↑ Makarov, Valeri V. (October 2003), "The 100 Brightest X-Ray Stars within 50 Parsecs of the Sun", The Astronomical Journal 126 (4): 1996–2008, doi:10.1086/378164, Bibcode: 2003AJ....126.1996M. 
  14. ↑ Trilling, D.E.; Stansberry, J.A.; Stapelfeldt, K.R.; Rieke, G.H.; Su, K.Y.L; Gray, R.O; Corbally, C.J; Bryden, G et al. (2007). "DEBRIS DISKS IN MAIN-SEQUENCE BINARY SYSTEMS". The Astrophysical Journal 658 (2): 1289-1311. doi:10.1086/511668. Bibcode: 2007ApJ...658.1289T. https://w.astro.berkeley.edu/~kalas/disksite/library/trilling07a.pdf. 



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