HD 8673

HD 8673 is a binary star in the northern constellation of Andromeda. It has an apparent magnitude and absolute magnitude of 6.34 and 3.56 respectively.[2] Based upon an annual parallax shift of 26.38 mas,[1] the system is located around 123.6 light years away. The system is moving further from the Earth with a heliocentric radial velocity of +19 km/s.[4] A sub-stellar companion was detected in 2005; it could either be an exoplanet or a brown dwarf.

HD 8673
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  01h 26m 08.78639s[1]
Declination +34° 34′ 46.9296″[1]
Apparent magnitude (V) 6.34[2]
Characteristics
Spectral type F7 V + M2 V[3]
B−V color index 0.500±0.004[2]
Astrometry
Radial velocity (Rv)19.20±0.71[4] km/s
Proper motion (μ) RA: 236.277±0.086[1] mas/yr
Dec.: −84.481±0.071[1] mas/yr
Parallax (π)26.3828 ± 0.0375[1] mas
Distance123.6 ± 0.2 ly
(37.90 ± 0.05 pc)
Absolute magnitude (MV)3.56[2]
Orbit[3]
Semi-major axis (a)35–60 AU
Eccentricity (e)< 0.5
Inclination (i)75–85°
Details[4]
HD 8673 A
Mass1.36±0.20 M☉
Radius1.521±0.049 R☉
Luminosity3.37+0.51
−0.44 L☉
Surface gravity (log g)4.21 cgs
Temperature6,340 K
Metallicity [Fe/H]0.15 dex
Rotational velocity (v sin i)26.9 km/s
Age1.5+2.1
−0.6 Gyr
HD 8673 B
Mass0.33–0.45[3] M☉
Temperature3,520-3,690[3] K
Other designations
BD+33°228, HD 8673, HIP 6702, HR 410, SAO 54695, PPM 66283, WDS J01262+3435AB, IRAS 01232+3418, 2MASS J01260875+3434471[5]
Database references
SIMBADdata

The primary component is an F-type main-sequence star with a stellar classification of F7 V.[3] It has 1.36 times the mass of the Sun and 1.52 times the Sun's radius. The star is around 1.5 billion years old and is spinning with a projected rotational velocity of 26.9 km/s. It is radiating 3.4 times the Sun's luminosity from its photosphere at an effective temperature of 6,340 K.[4]

Speckle interferometry measurements of this star between 2001 and 2008 showed a candidate stellar companion to this star, announced in 2011. It was unclear whether the pair formed a visual double or a binary system. The authors of the study estimated a class of K2 V, based upon a visual magnitude difference of 2.3±0.5.[6] Subsequent observations using adaptive options did not spot this companion and it was concluded this was a false detection. However, a low mass stellar companion was detected in a wide orbit. This red dwarf star has 0.33–0.45 times the mass of the Sun and is orbiting with a semimajor axis of 35–60 AU.[3]

Possible planetary system

An orbiting sub-stellar companion with a minimum mass 14 times that of Jupiter in a high-eccentricity orbit was discovered in 2005 and confirmed in 2010. This object orbits at 3 AU away from the primary star with a period of 1,634 days and an eccentricity of 0.7.[7]

The HD 8673 planetary system[7]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥14.2±1.6 MJ 3.02±0.15 1,634±17 0.723±0.016 — —

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.
  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.
  3. Roberts, Lewis C.; et al. (2015). "Know the Star, Know the Planet. IV. A Stellar Companion to the Host Star of the Eccentric Exoplanet HD 8673b". The Astronomical Journal. 149 (4). 144. arXiv:1502.06630. Bibcode:2015AJ....149..144R. doi:10.1088/0004-6256/149/4/144.
  4. Valenti, J. A.; Fischer, D. A. (2005). "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs". The Astrophysical Journal Supplement Series. 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500.
  5. "HD 6114". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 12, 2018.
  6. Mason, Brian D.; et al. (November 2011). "Know the star, know the planet. II. Speckle interferometry of exoplanet host stars". The Astronomical Journal. 142 (5): 6. arXiv:1109.4569. Bibcode:2011AJ....142..176M. doi:10.1088/0004-6256/142/5/176. 176.
  7. Hartmann, Michael; et al. (2010). "A Sub-stellar Companion around the F7 V Star HD 8673". The Astrophysical Journal. 717 (1): 348–356. Bibcode:2010ApJ...717..348H. doi:10.1088/0004-637X/717/1/348.
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