HD 129132

HD 129132 is a triple star[5] system in the northern constellation of Boötes. It is dimly visible to the naked eye with a combined apparent visual magnitude of 6.13.[2] The distance to this system is approximately 382 light years based on parallax, and it is drifting further away from the Sun with a radial velocity of +1.7 km/s.[1]

HD 129132
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Boötes
Right ascension 19h 40m 05.79185s[1]
Declination +18° 00′ 50.0046″[1]
Apparent magnitude (V) 6.13[2]
Characteristics
Spectral type G0V[3] or F4III[4]
B−V color index 0.434±0.004[2]
Astrometry
Radial velocity (Rv)+1.667±0.0024[1] km/s
Proper motion (μ) RA: +14.630[1] mas/yr
Dec.: −20.160[1] mas/yr
Parallax (π)8.5307 ± 0.1848[1] mas
Distance382 ± 8 ly
(117 ± 3 pc)
Absolute magnitude (MV)0.82
Orbit[5]
PrimaryA
CompanionB
Period (P)101.606±0.003 d
Semi-major axis (a)≥26.4±0.2 Gm
Eccentricity (e)0.117±0.007
Periastron epoch (T)2,442,478.0±0.8 HJD
Semi-amplitude (K1)
(primary)		19.0±0.1 km/s
Orbit[5]
PrimaryAB
CompanionC
Period (P)3,385±7 d
Semi-major axis (a)0.074±0.001"
(407±6 Gm)
Eccentricity (e)0.073±0.010
Inclination (i)104.6±0.5°
Periastron epoch (T)2,442,880±40 HJD
Argument of periastron (ω)
(secondary)		91.4±4.1°
Semi-amplitude (K1)
(primary)		8.5±0.1 km/s
Details
A
Mass1.99[6] M☉
Radius17.0+1.7
−1.6[1] R☉
Luminosity236.1+5.9
−5.7[1] L☉
Surface gravity (log g)3.41[6] cgs
Temperature5,488+275
−258[1] K
Rotational velocity (v sin i)25.3[6] km/s
Age1.00[6] Gyr
Other designations
BD+22°2731, HD 129132, HIP 71729, HR 5472, SAO 83458, WDS J14404+2159AB, GSC 01483-00948[7]
Database references
SIMBADdata

This system was found to be a spectroscopic binary by the Dominion Astrophysical Observatory in 1923. It was then shown to be a triple star system in 1937 by William E. Harper and Guy H. Blanchet.[8] The inner pair have an orbital period of 101.6 days and an eccentricity of 0.117, with the primary forming the visible component of this pair. The third component forms a visual system with the inner pair, orbiting with a period of 9.27 years and an eccentricity of 0.073.[5][9]

The primary component appears to be an aging giant star with a stellar classification of F4III,[4] although it has also been classed as a G-type main-sequence star of type G0V.[3] It is around a billion years old with twice the mass of the Sun.[6] The star has expanded to 17[1] times the Sun's radius and is radiating 236[1] times the luminosity of the Sun at an effective temperature of 5,488 K.[1] It is spinning with a projected rotational velocity of 25.3 km/s.[6]

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.
  3. Harlan, E. A.; Taylor, D. C. (March 1970). "MK classifications for F- and G-type stars. II". Astronomical Journal. 75 (2): 165–166. Bibcode:1970AJ.....75..165H. doi:10.1086/110956.
  4. Cowley, A. P.; Bidelman, W. P. (February 1979). "MK spectral types for some F and G stars". Publications of the Astronomical Society of the Pacific. 91: 83–86. Bibcode:1979PASP...91...83C. doi:10.1086/130446.
  5. Barlow, D. J.; Scarfe, C. D. (December 1991). "The Spectroscopic-Speckle Triple System HR 5472". Astronomical Journal. 102: 2098. Bibcode:1991AJ....102.2098B. doi:10.1086/116034.
  6. Luck, R. Earle (January 2017). "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants". The Astronomical Journal. 153 (1): 19. arXiv:1611.02897. Bibcode:2017AJ....153...21L. doi:10.3847/1538-3881/153/1/21. 21.
  7. "HD 129132". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-03.
  8. Harper, W. E.; Blanchet, G. H. (July 1937). "The spectroscopic orbits of H. R. 5472". Publications of the Dominion Observatory Ottawa. 7: 99-104. Bibcode:1937PDAO....7...99H.
  9. Malkov, O. Yu.; Tamazian, V. S.; Docobo, J. A.; Chulkov, D. A. (2012). "Dynamical Masses of a Selected Sample of Orbital Binaries". Astronomy & Astrophysics. 546: 5. Bibcode:2012A&A...546A..69M. doi:10.1051/0004-6361/201219774. A69.
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