Astronomy:Gamma Pyxidis

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Short description: K-type giant star in the constellation Pyxis
γ Pyxidis
Pyxis constellation map.svg
Red circle.svg
Location of γ Pyxidis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Pyxis
Right ascension  08h 50m 31.92282s[1]
Declination −27° 42′ 35.4421″[1]
Apparent magnitude (V) 4.010[2]
Characteristics
Spectral type K3 III[2]
U−B color index +1.368[3]
B−V color index +1.284[3]
Astrometry
Radial velocity (Rv)+24.5±0.7[4] km/s
Proper motion (μ) RA: −134.31[1] mas/yr
Dec.: 87.89[1] mas/yr
Parallax (π)15.73 ± 0.17[1] mas
Distance207 ± 2 ly
(63.6 ± 0.7 pc)
Absolute magnitude (MV)+0.00[5]
Details
Mass1.64[2] M☉
Radius21.87[6] R☉
Luminosity178[7] L☉
Surface gravity (log g)2.35[8] cgs
Temperature4,270[8] K
Metallicity [Fe/H]−0.05[8] dex
Age4.29±2.49[6] Gyr
Other designations
γ Pyx, CPD−27° 3442, FK5 332, GC 12216, HD 75691, HIP 43409, HR 3518, SAO 176559[9]
Database references
SIMBADdata

Gamma Pyxidis, Latinized from γ Pyxidis, is a single,[10] orange-hued star in the southern constellation Pyxis. It is visible to the naked eye, having an apparent visual magnitude of 4.010.[2] Based upon an annual parallax shift of 15.73 mas as seen from Earth,[1] it is located about 207 light years from the Sun. The star is moving further from the Sun with a radial velocity of +24.5 km/s.[4]

Properties

This is an evolved K-type giant star with a stellar classification of K3 III.[2] It is a red clump star on the horizontal branch,[11] indicating that it is generating energy through helium fusion at its core. The composition of the stellar atmosphere is similar to the Sun, having roughly the same abundance of iron in its spectrum.[12] The star has an estimated 1.64[2] times the mass of the Sun and has expanded to nearly 22[6] times the Sun's radius. At the age of around four billion years, it is radiating 178[7] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,270 K.[8]

Gamma Pyxidis is moving through the Galaxy at a speed of 54.2 km/s relative to the Sun. Its projected Galactic orbit carries it between 21,300 and 30,700 light years from the center of the Galaxy.[13][better source needed]

Naming

In Chinese, 天狗 (Tiān Gǒu), meaning Celestial Dog, refers to an asterism consisting of γ Pyxidis, e Velorum, f Velorum, β Pyxidis, α Pyxidis and δ Pyxidis. Consequently, γ Pyxidis itself is known as 天狗六 (Tiān Gǒu liù, English: the Sixth Star of Celestial Dog.)[14]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 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. http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2007A%2526A...474..653VFUL. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal 150 (3): 88, doi:10.1088/0004-6256/150/3/88, Bibcode: 2015AJ....150...88L. 
  3. ↑ 3.0 3.1 Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement 15: 459, doi:10.1086/190168, Bibcode: 1968ApJS...15..459G 
  4. ↑ 4.0 4.1 Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  5. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 6.2 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 & Astrophysics 574: A116, doi:10.1051/0004-6361/201322360, Bibcode: 2015A&A...574A.116R. 
  7. ↑ 7.0 7.1 Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics 352: 495–507, Bibcode: 1999A&A...352..495M 
  8. ↑ 8.0 8.1 8.2 8.3 Cenarro, A. J. (2007), "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters", Monthly Notices of the Royal Astronomical Society 374 (2): 664–690, doi:10.1111/j.1365-2966.2006.11196.x, Bibcode: 2007MNRAS.374..664C 
  9. ↑ "gam Pyx", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Gamma+Pyxidis, retrieved 2009-06-03 
  10. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  11. ↑ Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal 539 (2): 732–741, doi:10.1086/309278, Bibcode: 2000ApJ...539..732A. 
  12. ↑ Keenan, Philip C.; Barnbaum, Cecilia (June 1999), "Revision and Calibration of MK Luminosity Classes for Cool Giants by HIPPARCOS Parallaxes", The Astrophysical Journal 518 (2): 859–865, doi:10.1086/307311, Bibcode: 1999ApJ...518..859K 
  13. ↑ "Gamma Pyxidis (HIP 43409)". http://www.astrostudio.org/xhip.php?hip=43409. 
  14. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 17 日



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