Astronomy:Omega Eridani

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Short description: Star in the constellation Eridanus
ω Eridani
Location of ω Eridani (circled in red)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Eridanus
Right ascension  04h 52m 53.66995s[1]
Declination −05° 27′ 09.6972″[1]
Apparent magnitude (V) 4.37[2]
Characteristics
Spectral type A9 IVn[3]
U−B color index +0.12[2]
B−V color index +0.26[2]
Astrometry
Radial velocity (Rv)−8.3[4] km/s
Proper motion (μ) RA: −17.86[1] mas/yr
Dec.: +25.57[1] mas/yr
Parallax (π)13.88 ± 0.24[1] mas
Distance235 ± 4 ly
(72 ± 1 pc)
Absolute magnitude (MV)0.10[5]
Details
Radius6.7[6] R☉
Luminosity69[7] L☉
Surface gravity (log g)3.4[5] cgs
Temperature6,878[7] K
Metallicity [Fe/H]0.18[5] dex
Rotational velocity (v sin i)186[8] km/s
Other designations
ω Eri, BD−05°1068, 61 Eridani, HD 31109, HIP 22701, HR 1560, SAO 131568[9]
Database references
SIMBADdata

Omega Eridani (ω Eri) is a single[10] star in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude is 4.37.[2] The distance to this star, as determined by the parallax method, is around 235 light years.

It is an A-type subgiant star with a stellar classification of A9 IVn,[3] where the 'n' suffix indicates a broad ("nebulous") absorption due to rotation. The projected rotational velocity is 186[8] km/s.[8] This gives the star an oblate shape with an equator that is 13% wider than the polar radius. The angular size of Omega Eridani is 0.87 mas.[11] At an estimated distance of the star, this yields a physical size of around 6.7 times the radius of the Sun.[6]

Omega Eridani was long thought to be a single-lined spectroscopic binary system, with an orbital period of 3,057 days (8.4 years) and an eccentricity of 0.46.[12] However, newer and higher-quality radial velocity observations find no evidence for a companion, casting serious doubt on the status of Omega Eridani as a binary star.[10]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data (SIMBAD), Bibcode: 1986EgUBV........0M. 
  3. ↑ 3.0 3.1 Abt, Helmut A.; Morrell, Nidia I. (July 1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", Astrophysical Journal Supplement 99: 135, doi:10.1086/192182, Bibcode: 1995ApJS...99..135A. 
  4. ↑ De Bruijne, J. H. J.; Eilers, A.-C. (2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics 546: A61, doi:10.1051/0004-6361/201219219, Bibcode: 2012A&A...546A..61D. 
  5. ↑ 5.0 5.1 5.2 Giridhar, S. et al. (August 2013), "Identification of metal-poor stars using the artificial neural network", Astronomy & Astrophysics 556: 11, doi:10.1051/0004-6361/201219918, A121, Bibcode: 2013A&A...556A.121G. 
  6. ↑ 6.0 6.1 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1, https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41.  The radius (R*) is given by:
    2⋅R*=(72⋅0.87⋅10−3) AU0.0046491 AU/R⨀≈13.4⋅R⨀
  7. ↑ 7.0 7.1 McDonald, I. et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–57, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M. 
  8. ↑ 8.0 8.1 8.2 Royer, F. et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics 463 (2): 671–682, doi:10.1051/0004-6361:20065224, Bibcode: 2007A&A...463..671R. 
  9. ↑ "* ome Eri -- Spectroscopic binary". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+ome+Eri+--+Spectroscopic+binary. 
  10. ↑ 10.0 10.1 Merle, T.; Pourbaix, D.; Jorissen, A.; Siopis, C.; Eck, S. Van; Winckel, H. Van (2024-04-01). "Update of SB9 orbits using HERMES/Mercator radial velocities" (in en). Astronomy & Astrophysics 684: A74. doi:10.1051/0004-6361/202345918. ISSN 0004-6361. Bibcode: 2024A&A...684A..74M. https://www.aanda.org/articles/aa/full_html/2024/04/aa45918-23/aa45918-23.html. 
  11. ↑ van Belle, Gerard T., Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review 20 (1): 51, doi:10.1007/s00159-012-0051-2, Bibcode: 2012A&ARv..20...51V. 
  12. ↑ Abt, Helmut A.; Boonyarak, Chayan (November 2004), "Tidal Effects in Binaries of Various Periods", The Astrophysical Journal 616 (1): 562–566, doi:10.1086/423795, Bibcode: 2004ApJ...616..562A. 



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