20 Aquarii

20 Aquarii, abbreviated 20 Aqr, is a star in the constellation Aquarius. 20 Aquarii is the Flamsteed designation. It is a dim star with an apparent visual magnitude of 6.38.[2] Based upon an annual parallax shift of 15.34 mas,[1] it is located 213 light years away but is moving closer to the Earth with a heliocentric radial velocity of −23 km/s.[5] The star is predicted to come to within 110 light-years in around 1.9 million years.[2]

20 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  21h 24m 51.67515s[1]
Declination −03° 23′ 54.0858″[1]
Apparent magnitude (V) 6.38[2]
Characteristics
Spectral type F0 V[3] or F0 III[4]
B−V color index 0.334±0.002[2]
Astrometry
Radial velocity (Rv)−23.2±2.9[5] km/s
Proper motion (μ) RA: −6.125[1] mas/yr
Dec.: −49.515[1] mas/yr
Parallax (π)15.3426 ± 0.0730[1] mas
Distance213 ± 1 ly
(65.2 ± 0.3 pc)
Absolute magnitude (MV)2.37[2]
Details
Mass1.52[6] M☉
Luminosity9.38[2] L☉
Surface gravity (log g)4.17[6] cgs
Temperature7,314±249[6] K
Rotational velocity (v sin i)92[7] km/s
Age761[6] Myr
Other designations
BD−05° 5444, GC 29976, HD 203843, HIP 105729, HR 8192, SAO 145376[8]
Database references
SIMBADdata

This is an F-type main-sequence star with a stellar classification of F0 V.[3] (Cowley and Fraquelli [1974] had given it a class of F0 III.)[4] It is a suspected[9] chemically peculiar Am star showing metallic lines.[10] It is 761[6] million years old with a high projected rotational velocity of 92 km/s.[7] The star has 1.52[6] times the mass of the Sun and is radiating 9[2] times the Sun's luminosity from its photosphere at an effective temperature of about 7,314 K.[6]

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. 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.
  3. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
  4. Cowley, A.; Fraquelli, D. (1974), "MK Spectral Types for Some Bright F Stars", Publications of the Astronomical Society of the Pacific, 86 (509): 70, Bibcode:1974PASP...86...70C, doi:10.1086/129562.
  5. 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.
  6. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  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:1201.2052, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943.
  8. "20 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 23, 2018.
  9. Renson, P.; Manfroid, J. (2009), "Catalogue of Ap, HgMn and Am stars", Astronomy and Astrophysics, 498 (3): 961, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788.
  10. Paunzen, E.; et al. (February 2013), "A photometric study of chemically peculiar stars with the STEREO satellites - II. Non-magnetic chemically peculiar stars", Monthly Notices of the Royal Astronomical Society, 429 (1): 119–125, arXiv:1211.1535, Bibcode:2013MNRAS.429..119P, doi:10.1093/mnras/sts318.
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