HD 163840

HD 163840 is a binary star[6] system in the northern constellation of Hercules. It has a combined apparent visual magnitude of 6.45,[1] which falls just below the brightness level that is visible to the naked eye for people with normal eyesight. An annual parallax shift of 35.40[1] mas provides a distance estimate of about 92 light years. The system is moving closer to the Sun with a radial velocity of −33 km/s.[4] In about 769,000 years, it will make perihelion at a separation of around 27.2 ly (8.33 pc).[8]

HD 163840
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension  17h 57m 14.33667s[1]
Declination +23° 59′ 44.5562″[1]
Apparent magnitude (V) 6.4543±0.0005[1] (6.30 + 7.90)[2]
Characteristics
Spectral type G2 V + K2 V[3]
B−V color index 0.642±0.006[1]
Astrometry
Radial velocity (Rv)−32.83±0.07[4] km/s
Proper motion (μ) RA: −17.79±0.33[1] mas/yr
Dec.: +73.56±0.47[1] mas/yr
Parallax (π)35.40 ± 0.62[1] mas
Distance92 ± 2 ly
(28.2 ± 0.5 pc)
Absolute magnitude (MV)4.05[5]
Orbit[6]
Period (P)881.628±0.064 d
Semi-major axis (a)80.64 mas
Eccentricity (e)0.4165±0.0010
Inclination (i)72.83±0.47°
Longitude of the node (Ω)175.32±0.44°
Periastron epoch (T)55650.39 ± 0.38 (BJD−2400000)
Argument of periastron (ω)
(secondary)		135.46±0.16°
Details
HD 163840 A
Mass1.132±0.014[6] M☉
Luminosity2.031[3] L☉
Temperature5,860[3] K
Metallicity [Fe/H]0.06[5] dex
Age7.4[5] Gyr
HD 163840 B
Mass0.7421±0.0073[6] M☉
Luminosity0.648[3] L☉
Temperature4,780[3] K
Other designations
BD+24° 3283, GJ 4039, HD 163840, HIP 87895, HR 6697, SAO 85575, WDS J17572+2400A, Wolf 777[7]
Database references
SIMBADdata

R. K. Young of the Dominion Astrophysical Observatory was the first to recognize the variable radial velocity of this system.[9] In 1974, Harold A. McAlister and Philip A. Ianna identified it as a nearby G-type dwarf based on its spectroscopic properties.[10] McAlister et al. (1974) found it to be a spectroscopic binary[10] and the components were first resolved in 1976. A series of observations since that time allowed the system's orbital elements to be published by McAlister et al. (1995), along with estimates of the stellar masses of the two components.[11] These parameters have been further refined using improved instruments up through 2016.[6]

The pair of stars orbit each other with a period of 881.6 days (2.414 a) and an eccentricity of 0.417. The plane of their orbit is inclined by an angle of 73° to the line of sight from the Earth, with a semimajor axis having an angular value of 80.64 mas.[6] The close, eccentric orbit of the pair does not permit a stable planetary orbit in the habitable zone of either component.[3]

The primary, component A, is a magnitude 6.30[2] G-type main-sequence star with a stellar classification of G2 V.[3] It has 1.13[6] times the mass of the Sun and is radiating double the Sun's luminosity from its photosphere at an effective temperature of 5,860 K.[3] Component B, the magnitude 7.90[2] secondary, is a smaller K-type main-sequence star with a class of K2 V.[3] It has 0.74[6] times the Sun's mass and shines with 0.65[3] times the Sun's luminosity at an effective temperature of 4,780 K.[3] The system as a whole may be around 7.4[5] billion years old with a slightly higher metallicity than the Sun. The system displays solar-like variability.[12]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
  3. Eggl, S.; et al. (2012), "Circumstellar habitable zones of binary-star systems in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 428 (4): 3104, arXiv:1210.5411, Bibcode:2013MNRAS.428.3104E, doi:10.1093/mnras/sts257.
  4. Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424: 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
  5. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191.
  6. Kiefer, F.; et al. (May 2016), "Masses of the components of SB2 binaries observed with Gaia - III. Accurate SB2 orbits for 10 binaries and masses of HIP 87895", Monthly Notices of the Royal Astronomical Society, 458 (3): 3272−3281, arXiv:1603.02861, Bibcode:2016MNRAS.458.3272K, doi:10.1093/mnras/stw545.
  7. "HD 163840". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-01-12.
  8. Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, A35.
  9. Culver, R.; et al. (September 1980), "HR 6697: A Nearby G-Star Binary System", Bulletin of the American Astronomical Society, 12: 850, Bibcode:1980BAAS...12..850C.
  10. McAlister, Harold A.; Ianna, Philip A. (October 1974), "Possible Nearby F and G Dwarfs", Publications of the Astronomical Society of the Pacific, 86 (513): 769, Bibcode:1974PASP...86..769M, doi:10.1086/129672.
  11. McAlister, H. A.; et al. (July 1995), "Binary Star Orbits from Speckle Interferometry. VI. The Nearby Solar-Type Speckle-Spectroscopic Binary HR 6697", Astronomical Journal, 110: 366, Bibcode:1995AJ....110..366M, doi:10.1086/117527.
  12. Hall, Jeffrey C.; et al. (March 2007), "The Activity and Variability of the Sun and Sun-like Stars. I. Synoptic Ca II H and K Observations", The Astronomical Journal, 133 (3): 862–881, Bibcode:2007AJ....133..862H, doi:10.1086/510356.
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