Phi1 Orionis

Phi1 Orionis, is a binary star system in the constellation Orion, positioned less than a degree to the south of Meissa.[10] It is visible to the naked eye with an apparent visual magnitude of 4.42.[2] The distance to this system, based upon an annual parallax shift of 3.0 mas,[1] is around 1,090 light years.

For other stars with this Bayer designation, see Phi Orionis.
φ1 Orionis
φ1 (circled) in the constellation Orion.
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 05h 34m 49.23804s[1]
Declination +09° 29′ 22.4878″[1]
Apparent magnitude (V) 4.42[2]
Characteristics
Spectral type B0 III[3]
U−B color index −0.97[2]
B−V color index −0.15[2]
Astrometry
Radial velocity (Rv)+33.2[4] km/s
Proper motion (μ) RA: +0.27[1] mas/yr
Dec.: −2.26[1] mas/yr
Parallax (π)3.00 ± 0.25[1] mas
Distance1,090 ± 90 ly
(330 ± 30 pc)
Absolute magnitude (MV)−3.53±0.30
Orbit[5]
Period (P)3,068.03 d
Eccentricity (e)0.22
Periastron epoch (T)2418051.8 JD
Argument of periastron (ω)
(secondary)		105°
Semi-amplitude (K1)
(primary)		13.3 km/s
Details[6]
Mass15.5±1.1 M☉
Radius6.3±1.0 R☉
Luminosity28,840 L☉
Surface gravity (log g)4.05±0.10 cgs
Temperature30,000±300 K
Rotational velocity (v sin i)20[7] km/s
Age7.2±0.8[8] Myr
Other designations
φ1 Ori, 37 Orionis, BD+09° 877, FK5 208, HD 36822, HIP 26176, HR 1876, SAO 112914.[9]
Database references
SIMBADdata
φ1 Orionis with nebulosity west of φ2 Orionis and south of λ Orionis

This is a single-lined[6] spectroscopic binary star system with an orbital period of 3,068 days and an eccentricity of 0.22.[5] It is a member of the young Lambda Orionis cluster[11] and is roughly 7 million years old.[8] The primary component is a B-type giant star with a stellar classification of B0 III.[3] It has over 15 times the mass of the Sun and around 6.3 times the Sun's radius.[6] Nothing is known about the secondary companion. It does not contribute a significant amount of light to the combined spectrum.[6]

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. Murdin, P.; Penston, M. V. (December 1977), "The Lambda Orionis association", Monthly Notices of the Royal Astronomical Society, 181: 657–665, Bibcode:1977MNRAS.181..657M, doi:10.1093/mnras/181.4.657.
  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, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., 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. Nieva, María-Fernanda; Przybilla, Norbert (2014), "Fundamental properties of nearby single early B-type stars", Astronomy & Astrophysics, 566: A7, arXiv:1412.1418, Bibcode:2014A&A...566A...7N, doi:10.1051/0004-6361/201423373.
  7. 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.
  8. 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.
  9. "phi01 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-29.
  10. O'Meara, Stephen James (2007), Deep-Sky Companions: Hidden Treasures, Cambridge University Press, p. 146, ISBN 113946373X.
  11. Hernández, Jesús; Calvet, Nuria; Hartmann, L.; Muzerolle, J.; Gutermuth, R.; Stauffer, J. (December 2009), "Spitzer Observations of the λ Orionis Cluster. I. The Frequency of Young Debris Disks at 5 Myr", The Astrophysical Journal, 707 (1): 705–715, arXiv:0910.3884, Bibcode:2009ApJ...707..705H, doi:10.1088/0004-637X/707/1/705.
  • Kaler, James B. (February 10, 2012), "Phi-1 Orionis", Stars, University of Illinois, retrieved 2016-11-30.
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