70 Aquilae

70 Aquilae

Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	20^h 36^m 43.63394^s[1]
Declination	−02° 32′ 59.8341″[1]
Apparent magnitude (V)	4.903[2]
Characteristics
Spectral type	K4+ III Ba1,[3] K3 III,[4] or K5 II[5]
B−V color index	1.606±0.041[6]
Astrometry
Radial velocity (Rv)	−9.4±0.4[7] km/s
Proper motion (μ)	RA: +10.124[1] mas/yr Dec.: –15.604[1] mas/yr
Parallax (π)	3.4533 ± 0.3160 mas[1]
Distance	940 ± 90 ly (290 ± 30 pc)
Absolute magnitude (MV)	−3.05[6]
Details
Mass	6.2±0.6[8] M☉
Radius	102[9] R☉
Luminosity (bolometric)	4,072[2] L☉
Surface gravity (log g)	1.9[10] cgs
Temperature	3,900[2] K
Metallicity [Fe/H]	−0.294±0.093[11] dex
Rotational velocity (v sin i)	1.9[10] km/s
Age	63.1±17.8[8] Myr
Other designations
70 Aql, BD−03° 496, FK5 3648, HD 196321, HIP 101692, HR 7873, SAO 144624[12]
Database references
SIMBAD	data

70 Aquilae, abbreviated 70 Aql, is a single[13] orange-hued star in the equatorial constellation of Aquila. 70 Aquilae is its Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 4.90.[2] The distance to 70 Aquilae, as determined from its annual parallax shift of 3.5 mas,[1] is around 940 light years. The star is moving closer to the Earth with a heliocentric radial velocity of −9 km/s.[7]

Classification

Perkins et al. (1989) found a stellar classification of K4+ III Ba1[3] for this star, suggesting it is a K-type giant with abundance anomaly of barium.[14] Houk and Swift (1999) matched an ordinary giant with a class of K3 III.[4] Many sources[2][8][13][10][14] still use the 1991 Bright Star Catalogue classification of K5 II,[5] which instead suggests a bright giant star.

Size and temperature

The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 3.27±0.04 mas,[15] which, at its estimated distance, equates to a physical radius of roughly 102 times the radius of the Sun.[9] 70 Aquilae is about 63 million years old with 6 times the mass of the Sun.[8] It is radiating 4,072[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,900 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, S2CID 111387483.
3. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
4. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
5. Hoffleit, D.; Warren, Jr., W. H. (1991), "The Bright Star Catalogue", New Haven (5th Revised ed.), Astronomical Data Center, NSSDC/ADC, Bibcode:1964cbs..book.....H
6. 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, S2CID 119257644.
7. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
8. Tetzlaff, N.; et al. (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.
9. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:

   ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(289.6\cdot 3.27\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 204\cdot R_{\bigodot }\end{aligned}}}$

10. Domiciano de Souza, A.; et al. (November 2005), "Gravitational-darkening of Altair from interferometry", Astronomy and Astrophysics, 442 (2): 567–578, Bibcode:2005A&A...442..567D, doi:10.1051/0004-6361:20042476.
11. Taylor, B. J. (February 1999), "Catalogs of temperatures and [Fe/H] averages for evolved G and K stars", Astronomy and Astrophysics Supplement, 134 (3): 523–524, Bibcode:1999A&AS..134..523T, doi:10.1051/aas:1999153.
12. "69 Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 1, 2018.
13. Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
14. Gomez, A. E.; et al. (1997), "Absolute magnitudes and kinematics of barium stars", Astronomy and Astrophysics, 319: 881, Bibcode:1997A&A...319..881G.
15. Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.