Phi Geminorum

Phi Geminorum, Latinized from φ Geminorum, is a binary star[6] in the constellation Gemini, to the southwest of Pollux. It is visible to the naked eye with an apparent visual magnitude of 4.95.[2] Based upon an annual parallax shift of 14.66 mas,[1] this system is located around 220 light years from the Sun.

φ Geminorum
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Gemini
Right ascension  07h 53m 29.81390s[1]
Declination +26° 45′ 56.8252″[1]
Apparent magnitude (V) 4.95[2]
Characteristics
Spectral type A3 V[3]
U−B color index +0.08[2]
B−V color index +0.10[2]
Astrometry
Radial velocity (Rv)+8.0[4] km/s
Proper motion (μ) RA: −34.69[1] mas/yr
Dec.: -30.10[1] mas/yr
Parallax (π)14.66 ± 0.73[1] mas
Distance220 ± 10 ly
(68 ± 3 pc)
Absolute magnitude (MV)+0.81[5]
Orbit
Period (P)581.751 d[6]
Eccentricity (e)0.0[6]
Details
Mass1.9[7] M☉
Luminosity36.5[8] L☉
Surface gravity (log g)4.0[7] cgs
Temperature8,551±291[7] K
Rotational velocity (v sin i)165[9] km/s
Age637[7] Myr
Other designations
φ Gem, 83 Geminorum, BD+27° 1499, FK5 1207, HD 64145, HIP 38538, HR 3067, SAO 79774.[10]
Database references
SIMBADdata

The two components of this system have a circular orbit with a period of 582 days.[6] The primary component is an A-type main sequence star with a stellar classification of A3 V.[3] It is around 600 million years old and spinning relatively rapidly with a projected rotational velocity of 165[9] km/s. This rate of spin is giving the star an oblate shape with an equatorial bulge that is 6% larger than the polar radius.[3] The star has nearly double the mass of the Sun and radiates 36.5[8] times the solar luminosity from its outer atmosphere at an effective temperature of 8,551[7] K.

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. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  3. van Belle, Gerard T. (March 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.
  4. Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
  5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. Abt, Helmut A. (August 2005), "Observed Orbital Eccentricities", The Astrophysical Journal, 629 (1): 507–511, Bibcode:2005ApJ...629..507A, doi:10.1086/431207.
  7. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  8. 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.
  9. Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  10. "* phi Gem". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-12-08.
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