Astronomy:HD 20644

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

HD 20644 is a suspected binary star[6] 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.[1] The system is located at a distance of approximately 540 light years from the Sun based on parallax,[2] but is drifting closer with a radial velocity of −3 km/s.[1]

The visible component is an aging giant star with a stellar classification of K3IIIa Ba0.5,[4] 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).[8] Alternatively, this star may itself be on the AGB.[9] Analysis of the star gives a 74% probability that it is on the red giant branch, otherwise it would be a red clump star.[3]

HD 20644 is about 350 million years old with three[5] times the mass of the Sun and is spinning with a projected rotational velocity of 1.4 km/s.[6] 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.[5]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A.  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  3. ↑ 3.0 3.1 Reffert, Sabine et al. (2015), "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity", Astronomy and Astrophysics 574A (2): 116–129, doi:10.1051/0004-6361/201322360, Bibcode: 2015A&A...574A.116R. 
  4. ↑ 4.0 4.1 Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series 71: 245, doi:10.1086/191373, Bibcode: 1989ApJS...71..245K. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Baines, Ellyn K. et al. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal 155 (1): 30, doi:10.3847/1538-3881/aa9d8b, Bibcode: 2018AJ....155...30B. 
  6. ↑ 6.0 6.1 6.2 Lèbre, A. et al. (May 2006), "Lithium abundances and rotational behavior for bright giant stars", Astronomy and Astrophysics 450 (3): 1173–1179, doi:10.1051/0004-6361:20053485, Bibcode: 2006A&A...450.1173L. 
  7. ↑ "HD 20644". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+20644. 
  8. ↑ Yang, Guo-Chao et al. (January 2016), "Chemical abundance analysis of 19 barium stars", Research in Astronomy and Astrophysics 16 (1): 019, doi:10.1088/1674-4527/16/1/019, 19, Bibcode: 2016RAA....16...19Y. 
  9. ↑ 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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