HD 4732

HD 4732
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus[1][2]
Right ascension 00h 49m 13.949s[3]
Declination −24° 8′ 12.02″[3]
Apparent magnitude (V) 5.9[1][2]
Characteristics
Spectral type K2III[1][2]
U−B color index 0.72[1][2]
B−V color index 0.95[1][2]
R−I color index [1][2]
Astrometry
Proper motion (μ) RA: 78.54 ± 0.75[3] mas/yr
Dec.: –60.14 ± 0.79[3] mas/yr
Parallax (π)17.27 ± 0.61 mas[3]
Distance189 ± 7 ly
(58 ± 2 pc)
Details
Mass1.61 ± 0.05[4] M☉
Radius5.1 ± 0.1[4] R☉
Luminosity14.8 ± 0.2[4] L☉
Surface gravity (log g)3.22 ± 0.03[4] cgs
Temperature4994 ± 32[4] K
Age2.3 ± 0.2[4] Gyr
Other designations
CD−24 345，SAO 166602，HD 4732，HR 228, HIP 3834, 2MASS J00491393-2408119
Database references
SIMBADdata

HD 4732 is a red giant star of magnitude 5.9 located in the constellation Cetus. It is 189 light years from the Solar System.[3]

HD 4732 is located in the celestial Southern Hemisphere, although it can be observed from most regions of the Earth. Near Antarctica the star is circumpolar, while it is always below the horizon near the Arctic. Its magnitude of 5.9 places it at the limit of visibility to the naked eye, so observing this star with the naked eye is possible a clear sky and no Moon.

The best time to observe this star in the evening sky falls in the months between September and February, and from both hemispheres the period of visibility remains approximately the same, thanks to the star's position not far from the celestial equator.

The star is a red giant with an absolute magnitude of 2.14, and its radial velocity indicates that the star is moving away from the Solar System.

Planetary system

In November 2012 a double planetary system was announced orbiting around this star from radial velocity measurements at Okayama Astrophysical Observatory and Australian Astronomical Observatory. The planetary system has two giant planets with identical minimum masses of 2.4  times that of Jupiter with orbital periods of 360 days and 2732 days. The maximum mass of the planets cannot exceed 28 times that of Jupiter based on dynamical stability analysis for the system, if the planets are coplanar and prograde.[5]

The planetary system of HD 4732 was found to be stable in 2019.[6]

The HD 4732 planetary system[5]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius


b 2.37 ± 0.34 MJ 1.19 ± 0.05 360.2 ± 1.4 0.13 ± 0.06 — —
c 2.37 ± 0.38 MJ 4.60 ± 0.23 2732 ± 81 0.23 ± 0.07 — —

See also

Okayama Planet Search Program

References

  1. ^ a b c d e f "Pulsating variable Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2012-07-13.
  2. ^ a b c d e f "VizieR Detailed Page". Retrieved 2012-07-13.
  3. ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.Vizier catalog entry
  4. ^ a b c d e f Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575. A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951. S2CID 54555839.
  5. ^ a b Sato, Bun'ei; et al. (2013). "A Double Planetary System around the Evolved Intermediate-mass Star HD 4732". The Astrophysical Journal. 762 (1). 9. arXiv:1210.6798. Bibcode:2013ApJ...762....9S. doi:10.1088/0004-637X/762/1/9. S2CID 67838183.
  6. ^ Agnew, Matthew T; Maddison, Sarah T; Horner, Jonathan; Kane, Stephen R (June 2019). "Predicting multiple planet stability and habitable zone companions in the TESS era". Monthly Notices of the Royal Astronomical Society. 485 (4): 4703–4725. arXiv:1901.11297. doi:10.1093/mnras/stz345. Retrieved 28 April 2020.

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