Xi Orionis

Xi Orionis (ξ Orionis) is a binary star system in the northeastern part of the constellation of Orion, well above the red giant star Betelgeuse in the sky. It lies next to another blue main-sequence star, Nu Orionis, which is somewhat closer at 520 light-years' distance. The apparent visual magnitude of Xi Orionis is 4.47,[2] which is bright enough to be seen with the naked eye. The distance to this star, as determined using the parallax method, is roughly 610 light-years.[1]

ξ Orionis
Location of ξ Orionis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 06h 11m 56.39693s[1]
Declination +14° 12′ 31.5555″[1]
Apparent magnitude (V) 4.47[2]
Characteristics
Spectral type B3 IV[3]
U−B color index −0.65[2]
B−V color index −0.19[2]
Astrometry
Radial velocity (Rv)+19.30[4] km/s
Proper motion (μ) RA: +0.29[1] mas/yr
Dec.: −20.12[1] mas/yr
Parallax (π)5.37 ± 0.23 mas[1]
Distance610 ± 30 ly
(186 ± 8 pc)
Orbit[5]
Period (P)45.1 d
Eccentricity (e)0.26
Periastron epoch (T)2,441,962.3 JD
Argument of periastron (ω)
(secondary)		205°
Semi-amplitude (K1)
(primary)		22.4 km/s
Details
ξ Ori A
Mass6.7±0.1[3] M☉
Luminosity1,390[6] L☉
Temperature15,476[6] K
Rotational velocity (v sin i)160[7] km/s
Age32.1±4.3[3] Myr
Other designations
ξ Ori, 70 Orionis, BD+14° 1187, HD 42560, HIP 29426, HR 2199, SAO 95362[8]
Database references
SIMBADdata

This is a spectroscopic binary star system with an orbital period of 45.1 days and an eccentricity of 0.26.[5] The primary component is a B-type subgiant star with a stellar classification of B3 IV.[3] With an estimated age of just 32 million years,[3] it has a relatively high rate of spin, showing a projected rotational velocity of 160 km/s.[7] Xi Orionis has about 6.7 times the mass of the Sun,[3] and shines with 1,390 times the solar luminosity from its outer atmosphere at an effective temperature of 15,476 K.[6]

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.
  2. Crawford, D. L.; et al. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere", The Astronomical Journal, 76: 1058, Bibcode:1971AJ.....76.1058C, doi:10.1086/111220.
  3. Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  5. 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.
  6. 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.
  7. Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  8. "ksi Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-08.
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