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Omega Eridani 
Summary
Omega Eridani (ω Eri) is a binary star[9] system 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.
| Observation data Epoch J2000.0 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 mas[1] |
| Distance | 235 ± 4 ly (72 ± 1 pc) |
| Absolute magnitude (MV) | 0.10[5] |
| Orbit[6] | |
| Period (P) | 3,057 d |
| Eccentricity (e) | 0.46 |
| Periastron epoch (T) | 2419973.0 JD |
| Argument of periastron (ω) (secondary) | 227° |
| Semi-amplitude (K1) (primary) | 18.1 km/s |
| Details | |
| Radius | 6.7[7] R☉ |
| Luminosity | 69[8] L☉ |
| Surface gravity (log g) | 3.4[5] cgs |
| Temperature | 6,878[8] K |
| Metallicity [Fe/H] | 0.18[5] dex |
| Rotational velocity (v sin i) | 186[9] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a single-lined spectroscopic binary[11] system with an orbital period of 3,057 days (8.4 years) and an eccentricity of 0.46. The primary component 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[9] km/s.[9] This is giving 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.[12] At an estimated distance of the star, this yields a physical size of around 6.7 times the radius of the Sun.[7]
References edit
- ^ a b c d e 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.
- ^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
- ^ a b 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, Bibcode:1995ApJS...99..135A, doi:10.1086/192182.
- ^ De Bruijne, J. H. J.; Eilers, A.-C. (2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: A61, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347.
- ^ a b c Giridhar, S.; et al. (August 2013), "Identification of metal-poor stars using the artificial neural network", Astronomy & Astrophysics, 556: 11, arXiv:1307.6308, Bibcode:2013A&A...556A.121G, doi:10.1051/0004-6361/201219918, S2CID 118316149, A121.
- ^ Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
- ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
- ^ a b McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
- ^ a b c d Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
- ^ "* ome Eri -- Spectroscopic binary". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-03.
{{cite web}}: CS1 maint: postscript (link) - ^ Abt, Helmut A.; Boonyarak, Chayan (November 2004), "Tidal Effects in Binaries of Various Periods", The Astrophysical Journal, 616 (1): 562–566, Bibcode:2004ApJ...616..562A, doi:10.1086/423795.
- ^ van Belle, Gerard T., Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.
