HD 161840

HD 161840 is a single,[8] blue-white hued star in the southern zodiac constellation of Scorpius. It is faintly visible to the naked eye with an apparent visual magnitude of 4.79.[2] With an annual parallax shift of 6.5 mas[1] it is located roughly 500 light years from the Sun. It is moving closer with a heliocentric radial velocity of −13 km/s.[2]

HD 161840
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension  17h 48m 10.47559s[1]
Declination −31° 42′ 11.5636″[1]
Apparent magnitude (V) 4.79[2]
Characteristics
Spectral type B8 Ib/II[3]
B−V color index −0.028±0.023[2]
Astrometry
Radial velocity (Rv)−13.3±2.8[2] km/s
Proper motion (μ) RA: +6.845[1] mas/yr
Dec.: −8.161[1] mas/yr
Parallax (π)6.5831 ± 0.3618[1] mas
Distance500 ± 30 ly
(152 ± 8 pc)
Absolute magnitude (MV)−1.37[2]
Details
Mass3.93±0.08[4] M☉
Radius3.2[5] R☉
Luminosity565+59
−53[4] L☉
Surface gravity (log g)3.38[6] cgs
Temperature11066+77
−76[4] K
Rotational velocity (v sin i)24[4] km/s
Other designations
CD−31° 14609, HD 161840, HIP 87220, HR 6628, SAO 209303[7]
Database references
SIMBADdata

There has been some uncertainty as to the classification of this stage. Houk (1979) lists a stellar class of B8 Ib/II for HD 161840,[3] which corresponds to a B-type bright giant/lesser supergiant mix. Multiple studies still use an older classification of B8 V,[8][6][4] suggesting instead this is a B-type main-sequence star. Garrison and Gray (1994) assigned it a class of B8 III-IV,[9] which would put it on the subgiant/giant star track. It has an estimated 3.93[4] times the mass of the Sun and 3.2[5] times the Sun's radius. The star is radiating 565[4] times the Sun's luminosity from its photosphere at an effective temperature of 11,066 K.[4]

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, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1982mcts.book.....H.
  4. 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.
  5. Pasinetti Fracassini, L. E.; et al. (2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy & Astrophysics (3rd ed.), 367: 521–24, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  6. Hempel, M.; Holweger, H. (September 2003), "Abundance analysis of late B stars. Evidence for diffusion and against weak stellar winds", Astronomy and Astrophysics, 408: 1065–1076, Bibcode:2003A&A...408.1065H, doi:10.1051/0004-6361:20030889.
  7. "HD 161840". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-08-04.
  8. 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.
  9. Garrison, R. F.; Gray, R. O (1994), "The late B-type stars: Refined MK classification, confrontation with stromgren photometry, and the effects of rotation", The Astronomical Journal, 107: 1556, Bibcode:1994AJ....107.1556G, doi:10.1086/116967.
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