5 Aquilae

5 Aquilae (abbreviated 5 Aql) is a quadruple star[3] system in the constellation of Aquila. 5 Aquilae is the Flamsteed designation. The combined apparent visual magnitude of the system is 5.9,[2] which means it is faintly visible to the naked eye. With an annual parallax shift of 8.94 mas,[1] the distance to this system is estimated as approximately 360 light-years (110 parsecs), albeit with a 13% margin of error.

5 Aquilae
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 18h 46m 28.58278s[1]
Declination –00° 57′ 41.9006″[1]
Apparent magnitude (V) 5.90[2] (5.92/7.65)[3]
Characteristics
Spectral type A2 Vm + ? + F3 Vm[3][4]
U−B color index +0.12[2]
B−V color index +0.131[1]
Astrometry
Radial velocity (Rv)+17.4[5] km/s
Proper motion (μ) RA: +20.44[1] mas/yr
Dec.: –21.54[1] mas/yr
Parallax (π)8.94 ± 1.14[1] mas
Distanceapprox. 360 ly
(approx. 110 pc)
Orbit[6]
Primary5 Aql Aa
Companion5 Aql Ab
Period (P)33.65 ± 0.78 yr
Semi-major axis (a)0.219 ± 0.016″
Eccentricity (e)0.333 ± 0.054
Inclination (i)97.9 ± 1.4°
Longitude of the node (Ω)174.3 ± 1.9°
Periastron epoch (T)1989.71 ± 0.76
Argument of periastron (ω)
(secondary)		251.7 ± 5.9°
Details
Rotational velocity (v sin i)71[7] km/s
Other designations
BD–01 3559, HD 173654, HR 7059, WDS 18465-0058.[8][9]
5 Aql A: HIP 92117, SAO 142606.[8]
5 Aql B: HIP 92118, SAO 142607.[9]
Database references
SIMBAD5 Aql
5 Aql A
5 Aql B

Two of the components of this system, 5 Aquilae Aa and Ab, are Am stars. That is, they are chemically peculiar stars that show unusual abundances of elements other than hydrogen and helium. The two orbit each other with a period lasting 33.65 years at an eccentricity of 0.33. One of these stars is itself a close spectroscopic binary, with a 4.765 day period and a nearly circular orbit that has an eccentricity of just 0.02.[6] The fourth component, 5 Aquilae B, is a magnitude 7.65 F-type main sequence star with a stellar classification of F3 Vm. It is at an angular separation of 12.71 arcseconds from the other members of the system.[3]

References
  1. van Leeuwen, F. (November 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.
  2. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  4. 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.
  5. Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E.
  6. Mason, Brian D.; Hartkopf, William I.; Tokovinin, Andrei (September 2010), "Binary Star Orbits. IV. Orbits of 18 Southern Interferometric Pairs", The Astronomical Journal, 140 (3): 735–743, Bibcode:2010AJ....140..735M, doi:10.1088/0004-6256/140/3/735. Preliminary orbit.
  7. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943, S2CID 14070763.
  8. "* 5 Aql A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-22.
  9. "* 5 Aql B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-22.
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