20 Aquilae

20 Aquilae, abbreviated 20 Aql, is an irregular variable[10] star in the equatorial constellation of Aquila. 20 Aquilae is its Flamsteed designation. It ranges in magnitude from a peak of 5.33 down to 5.36, which is bright enough for the star to be visible to the naked eye.[11] The estimated distance to this star is around 920 light years, based upon an annual parallax shift of 3.5 mas.[1] The star is moving closer to the Earth with a heliocentric radial velocity of −23 km/s.[6]

20 Aquilae
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 12m 40.71201s[1]
Declination −07° 56′ 22.2650″[1]
Apparent magnitude (V) 5.362[2]
Characteristics
Spectral type B3 V,[3] B3 IV,[4] or B2/3 II[5]
B−V color index +0.088[2]
Astrometry
Radial velocity (Rv)−23.0±0.7[6] km/s
Proper motion (μ) RA: +14.040[1] mas/yr
Dec.: –6.814[1] mas/yr
Parallax (π)3.5374 ± 0.1720[1] mas
Distance920 ± 40 ly
(280 ± 10 pc)
Absolute magnitude (MV)−2.02[7]
Details
Mass8.6±0.2[8] M☉
Luminosity (bolometric)7,284[2] L☉
Temperature18,700[2] K
Rotational velocity (v sin i)133±6[3] km/s
Age27.9±4.1[8] Myr
Other designations
20 Aql, NSV 11808, BD−08° 4887, GC 26461, HD 179406, HIP 94385, HR 7279, SAO 143134[9]
Database references
SIMBADdata

There has been some disagreement over the stellar classification of this star. Buscombe (1962) listed a class of B3 IV,[4] which suggests a B-type subgiant star that has exhausted the hydrogen at its core and is expanding off the main sequence. Lesh (1968)[12] and Braganca et al. (2012)[3] matched a B-type main sequence star with a class of B3 V. However, Houk and Swift (1999) found a class of B2/3 II,[5] indicating this is an evolved bright giant.

The star is about 28[8] million years old with a high rate of spin, showing a projected rotational velocity of 133 km/s.[3] It has 8.6[8] times the mass of the Sun and is radiating 7,284 times the Sun's luminosity from its photosphere at an effective temperature of 18,700 K.[2]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355.
  3. Bragança, G. A.; et al. (November 2012), "Projected Rotational Velocities and Stellar Characterization of 350 B Stars in the Nearby Galactic Disk", The Astronomical Journal, 144 (5): 10, arXiv:1208.1674, Bibcode:2012AJ....144..130B, doi:10.1088/0004-6256/144/5/130, 130.
  4. Buscombe, W. (1962), "Spectral classification of Southern fundamental stars", Mount Stromlo Observatory Mimeogram, 4, Bibcode:1962MtSOM...4....1B.
  5. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
  6. Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  7. 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.
  8. Tetzlaff, N.; et al. (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.
  9. "20 Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 29, 2018.
  10. Lefèvre, L.; Marchenko, S. V.; Moffat, A. F. J.; Acker, A. (2009), "A systematic study of variability among OB-stars based on HIPPARCOS photometry", Astronomy and Astrophysics, 507 (2): 1141–1201, Bibcode:2009A&A...507.1141L, doi:10.1051/0004-6361/200912304, ISSN 0004-6361.
  11. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S.
  12. Lesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?", Astrophysical Journal Supplement, 17: 371, Bibcode:1968ApJS...17..371L, doi:10.1086/190179.
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