Phi Geminorum, Latinized from φ Geminorum, is a binary star[6] in the constellation Gemini, to the southeast 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.
| 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 mas[1] |
| Distance | 220 ± 10 ly (68 ± 3 pc) |
| Absolute magnitude (MV) | +0.81[5] |
| Orbit | |
| Period (P) | 581.751 d[6] |
| Eccentricity (e) | 0.0[6] |
| Details | |
| Mass | 1.9[7] M☉ |
| Luminosity | 36.5[8] L☉ |
| Surface gravity (log g) | 4.0[7] cgs |
| Temperature | 8,551±291[7] K |
| Rotational velocity (v sin i) | 165[9] km/s |
| Age | 637[7] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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
edit- ^ a b c d e f 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.
- ^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
- ^ a b c 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, S2CID 119273474.
- ^ Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
- ^ 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, S2CID 119257644.
- ^ a b c d Abt, Helmut A. (August 2005), "Observed Orbital Eccentricities", The Astrophysical Journal, 629 (1): 507–511, Bibcode:2005ApJ...629..507A, doi:10.1086/431207.
- ^ a b c d e 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, S2CID 33401607.
- ^ a b 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.
- ^ a b 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, S2CID 18475298.
- ^ "* phi Gem". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-12-08.
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