HR 6806

HR 6806
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 18h 09m 37.41628s[1]
Declination +38° 27′ 27.9959″[1]
Apparent magnitude (V) 6.40[2]
Characteristics
Spectral type K2 V[3]
U−B color index +0.585[2]
B−V color index +0.875[2]
Astrometry
Radial velocity (Rv)−19.315±0.0015[1] km/s
Proper motion (μ) RA: −316.520[1] mas/yr
Dec.: −468.214[1] mas/yr
Parallax (π)90.1264 ± 0.0200 mas[1]
Distance36.189 ± 0.008 ly
(11.096 ± 0.002 pc)
Absolute magnitude (MV)6.17[4]
Details
Mass0.791+0.014
−0.008[5] M☉
Radius0.79+0.02
−0.01[5] R☉
Luminosity0.35[5] L☉
Surface gravity (log g)4.53[3] cgs
Temperature4,900[3] K
Metallicity [Fe/H]−0.61[3] dex
Rotation42 d[6]
Rotational velocity (v sin i)4.82[7] km/s
Age5.8–7.1[8] Gyr
Other designations
BD+38°3095, GJ 706, HD 166620, HIP 88972, HR 6806, SAO 66700, LHS 3363[9]
Database references
SIMBADdata

HR 6806 or HD 166620 is a solitary, orange, main sequence, and Sun-like (K2 V) star located thirty-six light-years away,[10] 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. In 1988, it was noticed that the star had an inactive chromosphere, with a surface magnetic field strength of only 1,500 G.[6] From 1990 activity in the chromosphere increased, inline with a 16 year stellar cycle previously observed. But, sometime after 1994 (exact date unknown because of a data collection gap between 1995 and 2004) chromospheric activity greatly reduced, and has stayed flat for more than 16 years. As of 2022, the star appears to have entered the equivalent of a Maunder minimum.[10] The star is around six billion years of age.[8]

There was suspected to be a nearby very cool, and very dim, T9 to Y brown dwarf companion, WISE J180901.07+383805.4, at an angular separation of 769″, which would have corresponded to a projected separation of 8460 AU at the distance of HR 6806. However, with further observation it was found to be bluer than at first thought and more typical of a slightly brighter T7 dwarf, which would place it at a much greater 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.[11]

  1. ^ a b c d e f Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference MERMILLIOD was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference Gray was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Holmberg2009 was invoked but never defined (see the help page).
  5. ^ a b c d Cite error: The named reference Marsden2014 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference apj1_330_274 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference MartínezArnáiz2010 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference apj687 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference WrightIsaacson2022 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference apj760_2_152 was invoked but never defined (see the help page).