HD 179791

HD 179791 is suspected variable star[5] in the equatorial constellation of Aquila. It is a challenge to see with the naked eye even under good viewing conditions, having an apparent visual magnitude of 6.48.[2] The distance to HD 179791 can be estimated from its annual parallax shift of 5.3 mas,[1] which yields a value of 616 light years. It is moving further from the Earth with a heliocentric radial velocity of +16 km/s.[6] Astrometric measurements of the star show changes in motion that may indicate it is a member of a close binary system.[10]

HD 179791
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 13m 44.03146s[1]
Declination +05° 30′ 56.1725″[1]
Apparent magnitude (V) 6.48[2]
Characteristics
Evolutionary stage main sequence[3]
Spectral type A3 V[4]
U−B color index +0.10[2]
B−V color index +0.09[2]
Variable type suspected[5]
Astrometry
Radial velocity (Rv)+16.2[6] km/s
Proper motion (μ) RA: +6.819[1] mas/yr
Dec.: −9.809[1] mas/yr
Parallax (π)5.2966 ± 0.0569[1] mas
Distance616 ± 7 ly
(189 ± 2 pc)
Absolute magnitude (MV)0.66[7]
Details
Mass2.55±0.15[3] M☉
Radius2.5[8] R☉
Luminosity65.8+21.0
−16.0[3] L☉
Temperature8912+166
−162[3] K
Rotational velocity (v sin i)196[3] km/s
Other designations
NSV 11827, BD+05° 4081, HD 179791, HIP 94478, HR 7288, SAO 124410[9]
Database references
SIMBADdata

This is an A-type main-sequence star with a stellar classification of A3 V.[4] It is a suspected chemically peculiar star and formerly a candidate Lambda Boötis star.[11] The status as a Lambda Boötis star was reviewed and changed to non-member in 2015.[12] It is spinning rapidly with a projected rotational velocity of 196 km/s.[3] The star has 2.55[3] times the mass of the Sun and about 2.5[8] times the Sun's radius. It is radiating 66[3] times the Sun's luminosity from its photosphere at an effective temperature of 8,912 K.[3]

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. Cousins, A. W. J. (1965), "Photometric Data for Stars in the Equatorial Zone (Eighth List)", Monthly Notes of the Astronomical Society of Southern Africa, 24: 120, Bibcode:1965MNSSA..24..120C.
  3. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
  4. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  5. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  6. Gontcharov, G. A. (November 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, S2CID 119231169.
  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, S2CID 119257644.
  8. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  9. "HD 179791". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 6, 2018.
  10. 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
  11. Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars", Astronomy and Astrophysics, 498 (3): 961–966, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788.
  12. Cheng, Kwang-Ping; et al. (January 2017), "Utilizing Synthetic Visible Spectra to Explore the Physical Basis for the Classification of Lambda Boötis Stars", The Astronomical Journal, 153 (1): 15, Bibcode:2017AJ....153...39C, doi:10.3847/1538-3881/153/1/39, 39.
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