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 mas[1]
Distance	1,050 ± 60 ly (320 ± 20 pc)
Orbit[5]
Period (P)	9.5191 d
Eccentricity (e)	0.03
Periastron epoch (T)	2,418,275.65±10.0
Argument of periastron (ω) (secondary)	165°
Semi-amplitude (K1) (primary)	25.8 km/s
Details
π4 Ori A
Mass	10.95±0.97[6] M☉
Radius	9.1[7] R☉
Luminosity	19,726[6] L☉
Surface gravity (log g)	3.59[8] cgs
Temperature	21,874±126[7] K
Metallicity [Fe/H]	−0.31[8] dex
Rotational velocity (v sin i)	38[9] km/s
Age	15.4±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
SIMBAD	data

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 nine 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, S2CID 18759600.
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", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
5. Pourbaix, D.; et al. (2004), "S_B⁹: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
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, S2CID 111387483.
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 (3): 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, S2CID 118362423.
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, S2CID 119278062.
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 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
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, vol. 268, no. S268, pp. 317–324, Bibcode:2010IAUS..268..317K, doi:10.1017/S1743921310004291.