Astronomy:Phi Andromedae

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Short description: Binary star in the constellation Andromeda
Phi Andromedae
Location of φ Andromedae (upper left).
Observation data
Equinox J2000.0]] (ICRS)
Constellation Andromeda
Right ascension  01h 09m 30.12562s[1]
Declination +47° 14′ 30.4594″[1]
Apparent magnitude (V) 4.25[2] (4.46/6.06)[3]
Characteristics
Spectral type B7 Ve[4] + B9 V[3]
U−B color index −0.34[2]
B−V color index −0.07[2]
R−I color index −0.05
Astrometry
Radial velocity (Rv)−0.1[5] km/s
Proper motion (μ) RA: +4.05[1] mas/yr
Dec.: −12.43[1] mas/yr
Parallax (π)4.55 ± 0.60[1] mas
Distanceapprox. 720 ly
(approx. 220 pc)
Absolute magnitude (MV)−2.41[6]
Orbit[7]
Companionφ And B
Period (P)554.3 ± 67.1y yr
Semi-major axis (a)0.573 ± 0.051″
Eccentricity (e)0.385 ± 0.043
Inclination (i)142.2 ± 2.8°
Longitude of the node (Ω)337.2 ± 3.2°
Periastron epoch (T)17,740 ± 1,837 HMJD
Argument of periastron (ω)
(secondary)		112.6 ± 9.1°
Details
φ And A
Luminosity882[6] L☉
Surface gravity (log g)3.150[8] cgs
Temperature13490[8] K
Rotational velocity (v sin i)75[9] km/s
Age63.1 ± 13.7[10] Myr
Other designations
Junnanmen, φ And, 42 And, BD+46 275, HD 6811, HIP 5434, HR 335, SAO 36972, PPM 43693, ADS 940[11]
Database references
SIMBADdata

Phi Andromedae, also named Junnanmen, is a binary star[3] system near the border of the northern constellation of Andromeda. This system has a combined apparent visual magnitude of 4.25[2] and is visible to the naked eye. Based upon parallax measurements made during the Hipparcos mission, this star system is located at a distance of about 720 light-years (220 parsecs) from Earth.[1]

Nomenclature

Phi Andromedae (Latinized from φ Andromedae, abbreviated φ And) is the star's Bayer designation.

In Chinese astronomy, φ Andromedae forms the single-star asterism Jūnnánmén (軍南門 or 军南门, "Southern Military Gate").[12][13] R. H. Allen's Star Names refers to this asterism as Keun Nan Mun, "the Camp's South Gate", and includes χ Andromedae in it,[14] but in Chinese sources χ Andromedae is a member of the Tian Dajiangjun (Heaven's Great General) asterism.[15] Another identification of Jūnnánmén is α Trianguli.[13]

The IAU Working Group on Star Names approved the name Junnanmen for Phi Andromedae A on 25 August 2025 and it is now so entered in the IAU Catalog of Star Names.[16]

Components

φ Andromedae in optical light

The 4.46[3] magnitude primary component is a Be star with a stellar classification of B7 Ve, indicating that it is a B-type main sequence star that shows prominent emission lines of hydrogen in its spectrum. These emission lines come from a flattened decretion disk of hot gas that is orbiting the host star.[4] The star is rotating rapidly with a projected rotational velocity of 75 km/s.[9] The pole of the star is inclined around 20° to the line of sight from the Earth.[4]

The 6.06 magnitude companion star is a B-type main sequence star with a classification of B9 V. On average the two stars are separated by about 0.6 arcseconds and have an orbital period of roughly 554 years. Based upon their orbital elements, the system has a combined mass of around 6.5±2.8 times the mass of the Sun.[7]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99): 99, Bibcode: 1966CoLPL...4...99J. 
  3. ↑ 3.0 3.1 3.2 3.3 Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  4. ↑ 4.0 4.1 4.2 Silaj, J. et al. (March 2010), "A Systematic Study of Hα Profiles of Be Stars", The Astrophysical Journal Supplement 187 (1): 228–250, doi:10.1088/0067-0049/187/1/228, Bibcode: 2010ApJS..187..228S. 
  5. ↑ Wilson, Ralph Elmer (1953), "General catalogue of stellar radial velocities", Carnegie Institute Washington D.C. Publication (Carnegie Institution of Washington), Bibcode: 1953GCRV..C......0W . Accessed 2007-05-14.
  6. ↑ 6.0 6.1 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 Muterspaugh, Matthew W. et al. (December 2010), "The Phases Differential Astrometry Data Archive. II. Updated Binary Star Orbits and a Long Period Eclipsing Binary", The Astronomical Journal 140 (6): 1623–1630, doi:10.1088/0004-6256/140/6/1623, Bibcode: 2010AJ....140.1623M. 
  8. ↑ 8.0 8.1 Soubiran, Caroline et al. (2016), "The PASTEL catalogue: 2016 version", Astronomy & Astrophysics 591: A118, doi:10.1051/0004-6361/201628497, Bibcode: 2016A&A...591A.118S. 
  9. ↑ 9.0 9.1 Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, doi:10.1086/340590, Bibcode: 2002ApJ...573..359A. 
  10. ↑ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 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, doi:10.1111/j.1365-2966.2010.17434.x, Bibcode: 2011MNRAS.410..190T. 
  11. ↑ "* phi And". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+phi+And. 
  12. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 9 日
  13. ↑ 13.0 13.1 "Junnanmen (军南门)". IAU Working Group on Star Names. https://xing.fmi.uni-jena.de/mediawiki/index.php/Junnanmen. 
  14. ↑ Allen, R. H. (1899), Star-names and Their Meanings, New York: G. E. Stechart, p. 39, https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Andromeda*.html. 
  15. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日
  16. ↑ "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/. 



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