18 Aquilae
Location of 18 Aquilae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 06m 58.60289s[1]
Declination +11° 04′ 16.4173″[1]
Apparent magnitude (V) 5.072
Characteristics
Spectral type B8 III[2]
U−B color index −0.44[3]
B−V color index −0.08[3]
Variable type Eclipsing[4]
Astrometry
Radial velocity (Rv)−18.6[5] km/s
Proper motion (μ) RA: −0.89[1] mas/yr
Dec.: −32.11[1] mas/yr
Parallax (π)6.43 ± 0.79 mas[1]
Distanceapprox. 510 ly
(approx. 160 pc)
Orbit[6]
PrimaryA
CompanionB
Period (P)205.16 yr
Semi-major axis (a)0.399″
Eccentricity (e)0.23
Inclination (i)134.3°
Orbit[6]
PrimaryAa
CompanionAb
Period (P)1.3023 d
Semi-amplitude (K1)
(primary)		27.6 km/s
Details
Aa
Mass5.6[6] M☉
Luminosity4,875[7] L☉
Rotational velocity (v sin i)50[2] km/s
Ab
Mass0.38[6] M☉
Luminosity12.7[7] L☉
B
Mass3.49[6] M☉
Other designations
Y Aquilae, 18 Aql, BD+10 3787, FK5 3525, HD 178125, HIP 93867, HR 7248, SAO 104488[8]
Database references
SIMBADdata

18 Aquilae (abbreviated 18 Aql) is a triple star[9] system in the constellation of Aquila. 18 Aquilae is the Flamsteed designation; it also bears the variable star designation Y Aquilae. It has an apparent visual magnitude of 5.07. The distance to this system can be estimated from the annual parallax shift of 6.43 mas, yielding a value of around 510 light-years (160 parsecs) away from Earth.

A light curve for Y Aquilae, plotted from TESS data[10]

The inner pair of stars in this system form a spectroscopic binary with a combined magnitude of 5.44 and an orbital period of 1.302 days. The primary component is a giant star with a stellar classification of B8 III.[2] Because the orbital plane is inclined near the line of sight, two form an eclipsing binary system. The eclipse of the primary component causes a 0.04 drop in magnitude, while the eclipse of the secondary results in a decrease of 0.03.[11] At an angular separation of 0.310 arcseconds is the magnitude 6.39 tertiary component.[9] This system has a high peculiar velocity of 29.7 ± 3.9 km/s relative to the neighboring stars.[12]

References

  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:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. ^ a b c Levato, H. (January 1975). "Rotational velocities and spectral types for a sample of binary systems". Astronomy and Astrophysics Supplement Series. 19: 91–99. Bibcode:1975A&AS...19...91L.
  3. ^ a b Osawa, K.; Hata, S. (1962). "Three-color photometry of B8-A2 stars (II)". Annals of the Tokyo Astronomical Observatory. 7: 209. Bibcode:1962AnTok...7..209O.
  4. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  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.
  6. ^ a b c d e Tokovinin, Andrei (2018-03-01). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series. 235 (1): 6. arXiv:1712.04750. Bibcode:2018ApJS..235....6T. doi:10.3847/1538-4365/aaa1a5. ISSN 0067-0049. S2CID 119047709.
  7. ^ a b De Greve, J. P.; Vanbeveren, D. (1980). "Close Binary Systems Before and after Mass Transfer - a Comparison of Observations and Theory". Astrophysics and Space Science. 68 (2): 433. Bibcode:1980Ap&SS..68..433D. doi:10.1007/BF00639709. S2CID 123281741.
  8. ^ "18 Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-25.
  9. ^ a b 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.
  10. ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  11. ^ Malkov, O. Yu.; et al. (February 2006). "A catalogue of eclipsing variables". Astronomy and Astrophysics. 446 (2): 785–789. Bibcode:2006A&A...446..785M. doi:10.1051/0004-6361:20053137. hdl:10995/73280.
  12. ^ 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. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873.

External links

Constellation of Aquila
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