Psi2 Orionis

Psi2 Orionis a binary star system in the equatorial constellation of Orion. It has an apparent visual magnitude of 4.60,[2] indicating that it is visible to the naked eye. Based upon an annual parallax shift of 2.87 mass, it is roughly 1,100 light years distant from the Sun.

For other stars with this Bayer designation, see Psi Orionis.
ψ2 Orionis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 05h 26m 50.22929s[1]
Declination +03° 05′ 44.4203″[1]
Apparent magnitude (V) 4.60[2]
Characteristics
Spectral type B2 IV[3] (B1 III + B2 V)[4]
U−B color index −0.94[2]
B−V color index −0.22[2]
Astrometry
Radial velocity (Rv)+12.0[5] km/s
Proper motion (μ) RA: +1.71[1] mas/yr
Dec.: −1.94[1] mas/yr
Parallax (π)2.87 ± 0.68[1] mas
Distanceapprox. 1,100 ly
(approx. 350 pc)
Orbit[6]
Period (P)2.526 d
Eccentricity (e)0.04
Periastron epoch (T)2437685.227 JD
Argument of periastron (ω)
(secondary)		285°
Semi-amplitude (K1)
(primary)		139.1 km/s
Semi-amplitude (K2)
(secondary)		219.0 km/s
Details
ψ2 Ori A
Mass9.85±0.54[3] M☉
Luminosity10,252[3] L☉
Temperature21,150[3] K
Rotational velocity (v sin i)110[7] km/s
Other designations
ψ2 Ori, 30 Orionis, BD+02° 962, HD 35715, HIP 25473, HR 1811, SAO 112775.[8]
Database references
SIMBADdata

This is a double-lined spectroscopic binary,[4] which means that the individual absorption lines of both components can be discerned. The pair orbit each other with a period of 2.526 days and a low eccentricity of 0.04.[6] The close orbit is causing their mutual gravitational interaction to distort the shapes of the stars, turning this system into an ellipsoidal variable.[9] The inclination of orbital plane is sufficiently low that the two stars form a grazing eclipsing binary. During the eclipse of the primary component, the visual magnitude is reduced by 0.06, whereas the secondary eclipse reduces the magnitude by 0.03.[10]

The combined spectrum of Psi2 Orionis matches that of a B-type subgiant star with a stellar classification of B2 IV.[3] The primary component is an evolved giant star with a class of B1 III, while the secondary is a B-type main sequence star with a classification of B2 V.[4]

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.
  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. Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355.
  4. 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  5. Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Washington, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
  6. Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
  7. Abt, Helmut A.; et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  8. "psi02 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-12-01.
  9. Beech, Martin (February 1989), "The ellipsoidal variables. IV - Light variations", Astrophysics and Space Science, 152 (2): 329–335, Bibcode:1989Ap&SS.152..329B, doi:10.1007/BF00636314.
  10. Lefèvre, L.; et al. (2009), "A systematic study of variability among OB-stars based on HIPPARCOS photometry", Astronomy and Astrophysics, 507 (2): 1141–1201, Bibcode:2009A&A...507.1141L, doi:10.1051/0004-6361/200912304, ISSN 0004-6361.
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