66 Aquilae

66 Aquilae, abbreviated 66 Aql, is a fifth-magnitude star in the constellation of Aquila. 66 Aquilae is its Flamsteed designation. It is visible to the naked eye, having an apparent visual magnitude of 5.44.[2] The star shows an annual parallax shift of 4.4 mas,[1] which provides a distance estimate of around 730 light years. It is moving closer to the Earth with a heliocentric radial velocity of −30 km/s.[4] The motion of the star over time suggests some displacement, which may indicate it is a close binary system.[8]

66 Aquilae
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension  20h 13m 13.87230s[1]
Declination −01° 00′ 33.7724″[1]
Apparent magnitude (V) 5.44[2]
Characteristics
Spectral type K5 III[3]
B−V color index 1.430±0.001[2]
Astrometry
Radial velocity (Rv)−30.1±1.7[4] km/s
Proper motion (μ) RA: +32.872[1] mas/yr
Dec.: –15.851[1] mas/yr
Parallax (π)4.4436 ± 0.3133[1] mas
Distance730 ± 50 ly
(230 ± 20 pc)
Absolute magnitude (MV)−1.20[2]
Details
Radius59[5] R☉
Luminosity634.65[2] L☉
Surface gravity (log g)1.84[6] cgs
Temperature4040[6] K
Metallicity [Fe/H]−0.20[6] dex
Other designations
66 Aql, BD−01° 3920, GC 28068, HD 192107, HIP 99631, HR 7720, SAO 144181[7]
Database references
SIMBADdata

This is an aging giant star with a stellar classification of K5 III,[3] which indicates it has exhausted the supply of hydrogen at its core and expanded off the main sequence. The measured angular diameter of this star, after correcting for limb darkening, is 2.44±0.03 mas.[9] At its estimated distance, this yields a physical size of roughly 59 times the radius of the Sun.[5] It is radiating 635[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,040 K,[6] giving the star an orange hue.

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. 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.
  5. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  6. McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
  7. "66 Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 1, 2018.
  8. Mason, Brian D.; Martin, Christian; Hartkopf, William I.; Barry, Donald J.; Germain, Marvin E.; Douglass, Geoffrey G.; Worley, Charles E.; Wycoff, Gary L.; Ten Brummelaar, Theo; Franz, Otto G. (1999), "Speckle Interferometry of New and Problem HIPPARCOS Binaries", The Astronomical Journal, 117 (4): 1890, Bibcode:1999AJ....117.1890M, doi:10.1086/300823
  9. Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039
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