HD 167665

HD 167665 is a yellow-white hued star in the southern constellation of Sagittarius. With an apparent visual magnitude of 6.39,[2] it is near the lower brightness limit for stars that are visible to the naked eye. Based upon an annual parallax shift of 32.56 mas as seen from Earth, it is located 100 light years from the Sun. The star is moving away from the Sun with a radial velocity of +8 km/s.[4]

HD 167665
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension 18h 17m 23.7552s[1]
Declination −28° 17′ 20.278″[1]
Apparent magnitude (V) 6.39[2]
Characteristics
Spectral type F9V Fe−0.8 CH−0.4[3]
U−B color index +0.00[2]
B−V color index +0.52[2]
Astrometry
Radial velocity (Rv)+7.8±0.7[4] km/s
Proper motion (μ) RA: +136.333[1] mas/yr
Dec.: −147.910[1] mas/yr
Parallax (π)32.56 ± 0.47[1] mas
Distance100 ± 1 ly
(30.7 ± 0.4 pc)
Absolute magnitude (MV)+3.94[5]
Orbit[6]
Period (P)4,385±64 d
Semi-major axis (a)> 5.47±0.05 AU
Eccentricity (e)0.337±0.005
Periastron epoch (T)2448140 ± 70 JD
Argument of periastron (ω)
(secondary)		225.0±1.1°
Semi-amplitude (K1)
(primary)		0.6098±0.0031 km/s
Details[7]
Mass1.03±0.01 M☉
Radius1.32±0.02 R☉
Luminosity2.45[5] L☉
Surface gravity (log g)4.13±0.03 cgs
Temperature6,080±15 K
Metallicity [Fe/H]−0.21±0.01 dex
Rotational velocity (v sin i)8[8] km/s
Age6.72±0.23 Gyr
Other designations
CD−28° 14408, HD 167665, HIP 89620, HR 6836, SAO 186593[9]
Database references
SIMBADdata

This star has a stellar classification of F9V Fe−0.8 CH−0.4,[3] which indicates this is an F-type main-sequence star with a spectrum that displays mild underabundances of iron and the CH molecule compared to normal stars of this temperature. It is a solar-type star with about the same mass as the Sun, but has a radius 32% greater.[7] The star is older than the Sun with an estimated age of 6.7 billion years,[7] and it is spinning with a projected rotational velocity of 8 km/s.[8] HD 167665 is radiating 2.45[5] times the Sun's luminosity from its photosphere at an effective temperature of 6,080 K.[7]

Based upon regular variations in radial velocity observed between 1996 and 2006, an orbiting companion was announced by the California and Carnegie Planet Search (CCPS) program in 2007. This perturbing object, designated HD 167665 b,[10] has an orbital period of twelve years with an eccentricity of 0.337. The semimajor axis of this orbit is more than 5.47 AU and the object has a mass of at least 50.3±0.4 MJ. Since the inclination of the orbit is unknown, the exact mass can not yet be determined. However, there is a 79% chance that the mass of the object constrains it to be a brown dwarf with a mass less than 82 MJ.[6]

References
  1. Gaia Collaboration; et al. (November 2016), "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties", Astronomy & Astrophysics, 595: 23, arXiv:1609.04172, Bibcode:2016A&A...595A...2G, doi:10.1051/0004-6361/201629512, A2.
  2. Stobie, R. S. (1970), "Photometry of bright southern Cepheids", Monthly Notices of the Royal Astronomical Society, 148: 1–15, Bibcode:1970MNRAS.148....1S, doi:10.1093/mnras/148.1.1.
  3. Gray, R. O.; et al. (2006), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc--The Southern Sample", The Astronomical Journal, 132: 161, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637.
  4. Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959.
  5. 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.
  6. Patel, Shannon G.; et al. (August 2007), "Fourteen New Companions from the Keck and Lick Radial Velocity Survey Including Five Brown Dwarf Candidates", The Astrophysical Journal, 665 (1): 744–753, arXiv:0704.3418, Bibcode:2007ApJ...665..744P, doi:10.1086/519066.
  7. Maldonado, J.; Villaver, E. (June 2017), "Searching for chemical signatures of brown dwarf formation", Astronomy & Astrophysics, 602: 15, arXiv:1702.02904, Bibcode:2017A&A...602A..38M, doi:10.1051/0004-6361/201630120, A38.
  8. Balachandran, Suchitra (May 1, 1990), "Lithium depletion and rotation in main-sequence stars", Astrophysical Journal, Part 1, 354: 310–332, Bibcode:1990ApJ...354..310B, doi:10.1086/168691.
  9. "HD 167665". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-10-27.
  10. Reffert, S.; Quirrenbach, A. (March 2011), "Mass constraints on substellar companion candidates from the re-reduced Hipparcos intermediate astrometric data: nine confirmed planets and two confirmed brown dwarfs", Astronomy & Astrophysics, 527: 22, arXiv:1101.2227, Bibcode:2011A&A...527A.140R, doi:10.1051/0004-6361/201015861, A140.
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