Psi2 Orionis

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For other stars with this Bayer designation, see Psi Orionis.
ψ2 Orionis
Location of ψ2 Orionis (circled in red)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 05h 26m 50.22932s[1]
Declination +03° 05′ 44.4222″[1]
Apparent magnitude (V) 4.55 (- 4.58) - 4.61[2]
Characteristics
Spectral type B2 IV[3] (B1 III + B2 V)[4]
U−B color index −0.94[5]
B−V color index −0.22[5]
Variable type Eclipsing[2]
Astrometry
Radial velocity (Rv)−11.8±0.1[6] km/s
Proper motion (μ) RA: +1.448[1] mas/yr
Dec.: −1.019[1] mas/yr
Parallax (π)2.9943±0.1533 mas[1]
Distance1140±13 ly
(351±4 pc)[6]
Absolute magnitude (MV)−2.71[7]
Orbit[6]
Period (P)2.525940(2) days
Semi-major axis (a)24 R☉[a]
Eccentricity (e)0.0467±0.0003
Inclination (i)65.9±0.1°
Periastron epoch (T)58469.9122(1) BJD
Argument of periastron (ω)
(primary)		340.7±0.3°
Semi-amplitude (K1)
(primary)		174.3±0.1 km/s
Semi-amplitude (K2)
(secondary)		265.6±0.3 km/s
Details[6]
ψ2 Ori A
Mass17.69±0.05 M☉
Radius5.27±0.02 R☉
Luminosity3,890 L☉
Surface gravity (log g)4.06±0.03 cgs
Temperature25,600±610 K
Metallicity [Fe/H] = −0.172±0.038 dex
Rotational velocity (v sin i)102±3 km/s
Age11.4[8] Myr
ψ2 Ori B
Mass11.61±0.05 M☉
Radius5.05±0.02 R☉
Luminosity10,000 L☉
Surface gravity (log g)4.28±0.04 cgs
Temperature21,000±630 K
Metallicity [Fe/H] = −0.172±0.038 dex
Rotational velocity (v sin i)77±4 km/s
Other designations
ψ2 Ori, 30 Orionis, BD+02°962, HD 35715, HIP 25473, HR 1811, SAO 112775.[9]
Database references
SIMBADdata

Psi2 Orionis a binary star system in the equatorial constellation of Orion. It has an apparent visual magnitude of 4.6, indicating that it is visible to the naked eye. Based upon an annual parallax shift of 2.87 mas, it is roughly 1,100 light years distant from the Sun.

A light curve for Psi2 Orionis plotted from TESS data[10]

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 0.0467.[6] The close orbit is causing their mutual gravitational interaction to distort the shapes of the stars, turning this system into an ellipsoidal variable.[11] 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.[12] The brightness variability has led to the star being classified as a pulsating Beta Cephei variable, but no evidence has been found of pulsations superimposed on the variability due to ellipsoidal rotations and eclipses.[13][8]

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]

Notes

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  1. ^ from a sin i / sin(i), with a sin i = 21.9 R☉ and i = 65.9°.

References

[edit]
  1. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/GCVS. Bibcode:2009yCat....102025S.
  3. ^ a b 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. S2CID 111387483.
  4. ^ a b c 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. S2CID 14878976.
  5. ^ a b 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.
  6. ^ a b c d e Cakirli, O.; Hoyman, B.; Ozdarcan, O.; Bilir, S. (2025-09-22). "Selected β Cephei pulsators in eclipsing binaries". arXiv:2509.18277 [astro-ph.EP].
  7. ^ Melnik, A. M.; Dambis, A. K. (2020). "Distance scale for high-luminosity stars in OB associations and in field with Gaia DR2. Spurious systematic motions". Astrophysics and Space Science. 365 (7): 112. arXiv:2006.14649. Bibcode:2020Ap&SS.365..112M. doi:10.1007/s10509-020-03827-0. S2CID 220128144.
  8. ^ a b Telting, J. H.; Abbott, J. B.; Schrijvers, C. (2001). "Apsidal motion and non-radial pulsations in <ASTROBJ>psi 2 Ori</ASTROBJ>". Astronomy and Astrophysics. 377: 104. Bibcode:2001A&A...377..104T. doi:10.1051/0004-6361:20011026-1.
  9. ^ "psi02 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-12-01.
  10. ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  11. ^ 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. S2CID 119488926.
  12. ^ 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.
  13. ^ Waelkens, C.; Rufener, F. (May 1983). "An observational study of the influence of close companions on the pulsations of beta Cephei stars". Astronomy and Astrophysics. 121: 45–50. Bibcode:1983A&A...121...45W.