Phi Aquilae

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Phi Aquilae
Diagram showing star positions and boundaries of the Aquila constellation and its surroundings
Cercle rouge 100%.svg

Location of φ Aquilae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 56m 14.25182s[1]
Declination +11° 25′ 25.3942″[1]
Apparent magnitude (V) +5.28[2]
Spectral type A1 IV[3]
U−B color index –0.02[2]
B−V color index +0.00[2]
Radial velocity (Rv) –27.2[4] km/s
Proper motion (μ) RA: +32.29[1] mas/yr
Dec.: +4.44[1] mas/yr
Parallax (π) 14.86 ± 0.25 mas
Distance 219 ± 4 ly
(67 ± 1 pc)
Absolute magnitude (MV) +1.14[5]
Period (P) 3.32068 days
Eccentricity (e) 0.025
Periastron epoch (T) JD 2423210.628
Argument of periastron (ω)
Semi-amplitude (K1)
37.2 km/s
Radius 1.8–2.5[7] R
Luminosity 34[5] L
Surface gravity (log g) 4.30[8] cgs
Temperature 9,509[8] K
Metallicity [Fe/H] +0.47[8] dex
Rotational velocity (v sin i) 27[9] km/s
Other designations
φ Aql, φ Aql, 61 Aql, BD+11° 4055, FK5 3590, HD 188728, HIP 98103, HR 7610, SAO 105438.[10]
Database references

Phi Aquilae, Latinized from φ Aquilae, is the Bayer designation of a binary star[11] system in the equatorial constellation of Aquila. It has an apparent visual magnitude of +5.28[2] and is visible to the naked eye. With an annual parallax shift of 14.86 mas,[1] this star is located at a distance of approximately 219 light-years (67 parsecs) from Earth.

Phi Aquilae is a single-lined spectroscopic binary with an orbital period of 3.32068 days.[6] The primary component is a subgiant star with a stellar classification of A1 IV.[3] The outer atmosphere has an effective temperature of 9,509 K,[8] giving it the white-hued appearance of an A-type star.[12] The orbiting companion may be the source of the X-ray emission from this system, as stars similar to the primary component do not generally produce detectable levels of X-rays.[13]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Oja, T. (April 1983), "UBV photometry of FK4 and FK4 supplement stars", Astronomy and Astrophysics Supplement Series, 52: 131–134, Bibcode:1983A&AS...52..131O. 
  3. ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819. 
  4. ^ Wilson, Ralph Elmer (1953), General catalogue of stellar radial velocities, Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W. 
  5. ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971Freely accessible, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. 
  6. ^ a b Lucy, L. B.; Sweeney, M. A. (August 1971), "Spectroscopic binaries with circular orbits", Astronomical Journal, 76: 544–556, Bibcode:1971AJ.....76..544L, doi:10.1086/111159. 
  7. ^ Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367: 521–524, arXiv:astro-ph/0012289Freely accessible, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451. 
  8. ^ a b c d Soubiran, C.; Le Campion, J.-F.; Cayrel de Strobel, G.; Caillo, A. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069Freely accessible, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247. 
  9. ^ Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785Freely accessible, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224. 
  10. ^ "phi Aql -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-21. 
  11. ^ 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, arXiv:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 
  12. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16 
  13. ^ De Rosa, R. J.; et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society, 415 (1): 854–866, arXiv:1103.4363Freely accessible, Bibcode:2011MNRAS.415..854D, doi:10.1111/j.1365-2966.2011.18765.x. 

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