HD 164427

HD 164427 is a star with a likely red dwarf companion in the southern constellation of Pavo. It has an apparent visual magnitude of 6.88,[2] placing it just below the nominal limit for visibility with the typical naked eye. The annual parallax shift of 23.5 mas[1] yields a distance estimate of 139 light-years (43 parsecs). It is moving further from the Earth with a heliocentric radial velocity of +3.4 km/s.[1]

HD 164427
Observation data
Epoch J2000      Equinox J2000
Constellation Pavo
Right ascension 18h 04m 42.58968s[1]
Declination −59° 12′ 34.4678″[1]
Apparent magnitude (V) 6.88[2]
Characteristics
Spectral type G0+V[3]
B−V color index 0.624±0.015[2]
Astrometry
Radial velocity (Rv)+3.40±0.25[1] km/s
Proper motion (μ) RA: −196.087[1] mas/yr
Dec.: −51.219[1] mas/yr
Parallax (π)23.4516 ± 0.1836 mas[1]
Distance139 ± 1 ly
(42.6 ± 0.3 pc)
Absolute magnitude (MV)3.98±0.06[4]
Orbit[5]
Period (P)108.53855±0.00033 d
Semi-major axis (a)0.513+0.015
−0.016 AU
Eccentricity (e)0.54944±0.00073
Inclination (i)9.340+0.066
−0.058°
Longitude of the node (Ω)337.69+0.41
−0.49°
Periastron epoch (T)2457368.358±0.017
Argument of periastron (ω)
(secondary)		−3.187+0.078
−0.070°
Semi-amplitude (K1)
(primary)		2.2162+0.0028
−0.0031 km/s
Details[5]
Mass1.19±0.14 M☉
Radius1.404±0.037 R☉
Luminosity2.66+0.48
−0.34 L☉
Surface gravity (log g)4.216+0.062
−0.069 cgs
Temperature6,220+310
−240 K
Metallicity [Fe/H]−0.06+0.22
−0.25 dex
Age6.6+1.3
−0.9[4] Gyr
HD 164427 B
Mass355.5+2.6
−2.9 MJup
Other designations
CD−59° 6780, GJ 700, HD 164427, HIP 88531, SAO 245217[6]
Database references
SIMBADdata

This is an inactive[7] G-type main-sequence star given a stellar classification of G0+V by Gray et al. (2006),[3] although Evans et al. (1964) classified it as a subgiant star with luminosity class IV.[7] It is 6.6 billion years old with 1.125 times the mass of the Sun and 1.40 times the Sun's radius.[8] The star is somewhat over-luminous for its class,[7] radiating 2.33[2] times the Sun's luminosity from its photosphere at an effective temperature of 5,876 K.[3]

Companions

In 2001, a brown dwarf candidate companion was announced by Anglo-Australian Planet Search program. It was detected by the Doppler velocity technique with an echelle spectrograph attached to the 3.92m Anglo-Australian Telescope.[7] A magnitude 12.60 companion star designated HD 164427 B lies at an angular separation of 28.90″ along a position angle of 336°, as of 2010.[9] This is a suspected common proper motion companion with 52% of the Sun's mass[10] and a physical separation of as much as 1,090 AU.[7]

HD 164427 b was initially thought to be a brown dwarf based on its minimum mass of 46 times that of Jupiter.[7] In 2023, an astrometric orbit for this object was published using data from Gaia, showing its true mass to be 0.34 M☉, making it a likely red dwarf star.[5] This stellar companion orbits at nearly half an astronomical unit or Earth-to-Sun distance away from its primary. The angular separation between the two stars as viewed from Earth is 11.76 milliarcseconds. It takes 108.55 Earth days to orbit eccentrically around HD 164427. It has a very high semi-amplitude of almost 1400 m/s, because this is a very massive object which exerts strong gravitational pull on its tugging star.[7]

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. Gaia DR2 record for this source at VizieR.
  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. S2CID 119257644.
  3. Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
  4. Holmberg, J.; et al. (July 2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". Astronomy and Astrophysics Supplement Series. 501 (3): 941–947. arXiv:0811.3982. Bibcode:2009A&A...501..941H. doi:10.1051/0004-6361/200811191. S2CID 118577511.
  5. Unger, N.; Ségransan, D.; et al. (October 2023). "Exploring the Brown Dwarf Desert with Precision Radial Velocities and Gaia DR3 Astrometric Orbits". Astronomy & Astrophysics. arXiv:2310.02758.
  6. "HD 164427". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-08-02.
  7. Tinney, C. G.; et al. (2001). "First Results from the Anglo-Australian Planet Search: A Brown Dwarf Candidate and a 51 Peglike Planet". The Astrophysical Journal. 551 (1): 507–511. arXiv:astro-ph/0012204. Bibcode:2001ApJ...551..507T. doi:10.1086/320097. hdl:2299/138. S2CID 7192024.
  8. Takeda, Genya; et al. (February 2007). "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog". The Astrophysical Journal Supplement Series. 168 (2): 297–318. arXiv:astro-ph/0607235. Bibcode:2007ApJS..168..297T. doi:10.1086/509763. S2CID 18775378.
  9. Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  10. Tokovinin, Andrei (April 2014). "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs". The Astronomical Journal. 147 (4): 14. arXiv:1401.6827. Bibcode:2014AJ....147...87T. doi:10.1088/0004-6256/147/4/87. S2CID 56066740. 87.
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