Pi4 Orionis

Pi4 Orionis (π4 Ori, π4 Orionis) is a binary star system in the western part of the Orion constellation. It is visible to the naked eye with an apparent visual magnitude of 3.7.[2] Based upon an annual parallax shift of 3.1 mass,[1] it is located roughly 1,050 light years from the Sun.

For other stars with this Bayer designation, see Pi Orionis.
π4 Orionis
Location of π4 Orionis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 04h 51m 12.36472s[1]
Declination +05° 36′ 18.3723″[1]
Apparent magnitude (V) 3.685[2]
Characteristics
Spectral type B2 III[3]
U−B color index −0.797[2]
B−V color index −0.180[2]
Astrometry
Radial velocity (Rv)23.3[4] km/s
Proper motion (μ) RA: −2.21[1] mas/yr
Dec.: +0.85[1] mas/yr
Parallax (π)3.10 ± 0.18[1] mas
Distance1,050 ± 60 ly
(320 ± 20 pc)
Orbit[5]
Period (P)9.5191 d
Eccentricity (e)0.03
Periastron epoch (T)2418275.65±10.0
Argument of periastron (ω)
(secondary)		165°
Semi-amplitude (K1)
(primary)		25.8 km/s
Details
π4 Ori A
Mass10.95±0.97[6] M☉
Radius9.1[7] R☉
Luminosity19,726[6] L☉
Surface gravity (log g)3.59[8] cgs
Temperature21,874±126[7] K
Metallicity [Fe/H]−0.31[8] dex
Rotational velocity (v sin i)38[9] km/s
Age15.4±1.0[10] Myr
Other designations
π4 Ori, 3 Orionis, BD+05°745, FK5 179, HD 30836, HIP 22549, HR 1552, SAO 112142[11]
Database references
SIMBADdata

This is a spectroscopic binary star system with an orbital period of 9.5 days and an eccentricity of 0.03.[5] The primary component is a B-type star with a stellar classification of B2 III.[3] The stellar spectrum of π4 Ori A shows a strong depletion of the element boron.[12] It has nearly 11[6] times the mass of the Sun and 9 times the Sun's radius.[7] The star is 15.4[10] million years old and has a projected rotational velocity of 38 km/s.[9] It shines with 19,726[6] times the solar luminosity from its outer atmosphere at an effective temperature of 21,874 k.[7]

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. Oja, T. (August 1985), "Photoelectric photometry of stars near the north Galactic pole. II", Astronomy and Astrophysics Supplement Series, 61: 331–339, Bibcode:1985A&AS...61..331O.
  3. Levato, H. (January 1975), "Rotational velocities and spectral types for a sample of binary systems", Astronomy and Astrophysics Supplement Series, 19: 91–99, Bibcode:1975A&AS...19...91L.
  4. Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  5. Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
  6. 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.
  7. Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601.
  8. Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247.
  9. Simón-Díaz, S.; Herrero, A. (2014), "The IACOB project. I. Rotational velocities in northern Galactic O- and early B-type stars revisited. The impact of other sources of line-broadening", Astronomy & Astrophysics, 562: A135, arXiv:1311.3360, Bibcode:2014A&A...562A.135S, doi:10.1051/0004-6361/201322758.
  10. Tetzlaff, N.; et al. (2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410: 190, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
  11. "pi.04 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-18.
  12. Kaufer, A. (April 2010), "Observations of light elements in massive stars", Light Elements in the Universe, Proceedings of the International Astronomical Union, IAU Symposium, 268, pp. 317–324, Bibcode:2010IAUS..268..317K, doi:10.1017/S1743921310004291.
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