Pi2 Orionis

Pi2 Orionis (π2 Ori, π2 Orionis) is the Bayer designation for a solitary star in the equatorial constellation of Orion. Although the Bright Star Catalogue lists this as a spectroscopic binary star system,[10] this does not appear to be the case.[11] It is visible to the naked eye with an apparent visual magnitude of 4.35.[2] Based upon an annual parallax shift of 14.53 mas,[1] it is located roughly 224 light-years away from the Sun.

For other stars with this Bayer designation, see Pi Orionis.
π2 Orionis
Location of π2 Orionis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 04h 50m 36.72298s[1]
Declination +08° 54′ 00.6493″[1]
Apparent magnitude (V) 4.35[2]
Characteristics
Spectral type A1 Vn[3]
U−B color index +0.03[2]
B−V color index +0.01[2]
Astrometry
Radial velocity (Rv)24[4] km/s
Proper motion (μ) RA: +1.41[1] mas/yr
Dec.: −29.91[1] mas/yr
Parallax (π)14.53 ± 0.38 mas[1]
Distance224 ± 6 ly
(69 ± 2 pc)
Absolute magnitude (MV)0.48[5]
Details
Radius2.7[6] R☉
Luminosity70[7] L☉
Surface gravity (log g)4.00±0.05[8] cgs
Temperature9,457±128[8] K
Metallicity [Fe/H]−0.20±0.10[8] dex
Rotational velocity (v sin i)261.4±13.5[5] km/s
Other designations
π2 Ori, 2 Orionis, BD+08°777, HD 30739, HIP 22509, HR 1544, SAO 112124[9]
Database references
SIMBADdata

This is an A-type main-sequence star with a stellar classification of A1 Vn,[3] where the 'n' indicates broad absorption lines due to rotation. It is spinning rapidly with a projected rotational velocity of 261.4 km/s.[5] This is giving the star an oblate shape with an equatorial bulge that is 13% larger than the polar radius.[12] It is shining with 70[7] times the solar luminosity from its outer atmosphere at an effective temperature of 9,457 K.[8]

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. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  3. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  4. Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Washington, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
  5. Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
  6. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  7. 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.
  8. Wu, Yue; et al. (January 2011), "Coudé-feed stellar spectral library - atmospheric parameters", Astronomy and Astrophysics, 525: A71, arXiv:1009.1491, Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014, S2CID 53480665.
  9. "pi.02 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-16.
  10. Hoffleit, Dorrit (1964), Catalogue of Bright Stars (3rd ed.), New Haven, Conn: Yale University Observatory, Bibcode:1964cbs..book.....H.
  11. 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.
  12. Belle, G. T. (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.
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