HD 20644

HD 20644
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Aries
Right ascension 03h 20m 20.36111s[1]
Declination +29° 02′ 54.4451″[1]
Apparent magnitude (V) 4.47[2]
Characteristics
Spectral type K3IIIa Ba0.5[3]
B−V color index 1.555±0.020[2]
Astrometry
Radial velocity (Rv)−3.09±0.28[2] km/s
Proper motion (μ) RA: −7.71[1] mas/yr
Dec.: −16.91[1] mas/yr
Parallax (π)6.01 ± 0.25 mas[1]
Distance540 ± 20 ly
(166 ± 7 pc)
Absolute magnitude (MV)−1.63[2]
Details
Mass3.07±0.39[4] M☉
Radius65.70+2.66
−2.80[4] R☉
Luminosity1,576±199[4] L☉
Surface gravity (log g)2.00[4] cgs
Temperature4,485±108[4] K
Metallicity [Fe/H]−0.27±0.04[2] dex
Rotational velocity (v sin i)1.4[5] km/s
Age350±140[4] Myr
Other designations
BD+28°516, FK5 2234, HD 20644, HIP 15549, HR 999, SAO 75871[6]
Database references
SIMBADdata

HD 20644 is a suspected binary star[5] system in the constellation Aries. It has an orange hue and is visible to the naked eye with an apparent visual magnitude of 4.47.[2] The system is located at a distance of approximately 540 light years from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −3 km/s.[2]

The visible component is an aging giant star with a stellar classification of K3IIIa Ba0.5,[3] where the suffix notation indicates this is a mild barium star. The atmosphere of this star is enriched with s-process elements that are posited to have been transferred from what is now a white dwarf companion when it evolved along the asymptotic giant branch (AGB).[7] Alternatively, this star may itself be on the AGB.[8]

HD 20644 is about 350 million years old with three[4] times the mass of the Sun and is spinning with a projected rotational velocity of 1.4 km/s.[5] With the supply of hydrogen at its core exhausted, it has expanded to 66 times the Sun's radius. It is radiating 1,576 times the luminosity of the Sun from its photosphere at an effective temperature of 4,485 K.[4]

References

  1. ^ 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.
  2. ^ a b c d e f g 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. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  4. ^ a b c d e f g h Baines, Ellyn K.; et al. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal, 155 (1), 30, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b, S2CID 119427037.
  5. ^ a b c Lèbre, A.; et al. (May 2006), "Lithium abundances and rotational behavior for bright giant stars", Astronomy and Astrophysics, 450 (3): 1173–1179, Bibcode:2006A&A...450.1173L, doi:10.1051/0004-6361:20053485.
  6. ^ "HD 20644". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-12-22.
  7. ^ Yang, Guo-Chao; et al. (January 2016), "Chemical abundance analysis of 19 barium stars", Research in Astronomy and Astrophysics, 16 (1): 019, arXiv:1602.08704, Bibcode:2016RAA....16...19Y, doi:10.1088/1674-4527/16/1/019, S2CID 14474857, 19.
  8. ^ Mennessier, M. O.; et al. (October 1997), "Barium stars, galactic populations and evolution", Astronomy and Astrophysics, 326: 722–730, Bibcode:1997A&A...326..722M.

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