HR 6806

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HR 6806
Observation data
Epoch 2000      Equinox 2000
Constellation Hercules
Right ascension 18h 09m 37.41626s[1]
Declination +38° 27′ 27.9960″[1]
Apparent magnitude (V) 6.40[2]
Spectral type K2 V[3]
U−B color index +0.585[2]
B−V color index +0.875[2]
Radial velocity (Rv) −19.473 ± 0.028[4] km/s
Proper motion (μ) RA: −316.44[1] mas/yr
Dec.: −468.47[1] mas/yr
Parallax (π) 90.71 ± 0.30[1] mas
Distance 36.0 ± 0.1 ly
(11.02 ± 0.04 pc)
Mass 0.791+0.014
[5] M
Radius 0.79+0.02
[5] R
Luminosity 0.35[5] L
Surface gravity (log g) 4.53[3] cgs
Temperature 4,900[3] K
Metallicity [Fe/H] −0.61[3] dex
Rotation 42 d[6]
Rotational velocity (v sin i) 4.82[7] km/s
Age 5.8–7.1[8] Gyr
Other designations
BD+38 3095, GJ 706, HD 166620, HIP 88972, HR 6806, LHS 3363, SAO 66700.[9]
Database references

HR 6806 is a solitary, orange, main sequence (K2 V) star located thirty-six light-years away, in the constellation Hercules. The star is smaller than the Sun, with around 79% of the solar mass and radius, and 35% of the solar luminosity.[5] It appears to be rotating slowly with an estimated period of 42 days. The star has an inactive chromosphere, with a surface magnetic field strength of 1,500 G.[6]

There is a nearby brown dwarf, WISE J180901.07+383805.4, at an angular separation of 769″, which would correspond to a projected separation of 8460 AU at the distance of HR 6806. However, this is most likely a typical T7 dwarf, which would place it at a distance of 91 ly (28 pc)—ruling out a physical association. This is confirmed by the differing proper motion of the star and this object.[10]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data, SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b c d Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770Freely accessible, Bibcode:2006AJ....132..161G, doi:10.1086/504637. 
  4. ^ Soubiran, C.; et al. (April 2013), "The catalogue of radial velocity standard stars for Gaia. I. Pre-launch release", Astronomy & Astrophysics, 552: 11, arXiv:1302.1905Freely accessible, Bibcode:2013A&A...552A..64S, doi:10.1051/0004-6361/201220927, A64. 
  5. ^ a b c d Marsden, S. C.; et al. (November 2014), "A BCool magnetic snapshot survey of solar-type stars", Monthly Notices of the Royal Astronomical Society, 444 (4): 3517–3536, arXiv:1311.3374Freely accessible, Bibcode:2014MNRAS.444.3517M, doi:10.1093/mnras/stu1663. 
  6. ^ a b Basri, Gibor; Marcy, Geoffrey W. (July 1988), "Physical realism in the analysis of stellar magnetic fields", Astrophysical Journal, Part 1, 330: 274–285, Bibcode:1988ApJ...330..274B, doi:10.1086/166471. 
  7. ^ Martínez-Arnáiz, R.; et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter", Astronomy and Astrophysics, 520: A79, arXiv:1002.4391Freely accessible, Bibcode:2010A&A...520A..79M, doi:10.1051/0004-6361/200913725. 
  8. ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal, 687 (2): 1264–1293, arXiv:0807.1686Freely accessible, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785. 
  9. ^ "HR 6806 -- Variable Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2015-11-02. 
  10. ^ Luhman, Kevin L.; et al. (December 2012), "New M, L, and T Dwarf Companions to Nearby Stars from the Wide-field Infrared Survey Explorer", The Astrophysical Journal, 760 (2): 9, arXiv:1211.3977Freely accessible, Bibcode:2012ApJ...760..152L, doi:10.1088/0004-637X/760/2/152, 152. 

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