Alpha Columbae

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Alpha Columbae
Diagram showing star positions and boundaries of the Columba constellation and its surroundings
Cercle rouge 100%.svg

Location of α Columbae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Columba
Right ascension 05h 39m 38.94103s[1]
Declination −34° 04′ 26.7950″[1]
Apparent magnitude (V) 2.645[2]
Characteristics
Spectral type B7 IV[3]
U−B color index −0.44[2]
B−V color index −0.125[2]
R−I color index −0.09[4]
Astrometry
Radial velocity (Rv) +35.0[5] km/s
Proper motion (μ) RA: −1.58[1] mas/yr
Dec.: −24.82[1] mas/yr
Parallax (π) 12.48 ± 0.36[1] mas
Distance 261 ± 8 ly
(80 ± 2 pc)
Absolute magnitude (MV) −1.9
Details
Mass 4.5[6] M
Radius 5.8[7] R
Luminosity (bolometric) 1,000[6] L
Surface gravity (log g) 3.73[7] cgs
Temperature 12,963[7] K
Rotational velocity (v sin i) 176[8] km/s
Other designations
Alpha Columbae, α Col, CCDM J05396−3404 A, CD−34 2375, CPD−34 703, FK5 215, GC 7078, HD 37795, HIP 26634, HR 1956, NSV 2549, PPM 281732, SAO 196059.[9]
Database references
SIMBAD data

Alpha Columbae (α Columbae, α Col) is the Bayer designation for a third magnitude star in the southern constellation of Columba. It has the traditional name of Phact, which is derived from the Arabic term for "ring-necked dove". It has an apparent visual magnitude of 2.6,[2] making it the brightest member of Columba. Based upon parallax measurements made during the Hipparcos mission, Alpha Columbae is located at a distance of around 261 light-years (80 parsecs).[1]

Properties[edit]

This is believed to be a solitary star,[10][8] although it has a faint optical companion at an angular separation of 13.5 arcseconds, making it a double star.[11] The stellar classification of Alpha Columbae is B7 IV,[3] with the luminosity class of IV indicating it has evolved into a subgiant star. The spectrum shows it to be a Be star surrounded by a hot gaseous disk, which is generating emission lines because of hydrogen recombination.[12] Like most if not all such stars, it is rotating rapidly with a projected rotational velocity of 176 km s−1. The azimuthal equatorial velocity may be 457 km s−1.[8] It is a suspected Gamma Cassiopeiae type (GCAS) variable star, with its apparent magnitude varying from 2.62m to 2.66m.

Etymology[edit]

The proper name "Phact" (also Phad, Phaet, Phakt[12]) derived from the Arabic ألفاجتة - fākh(i)tah [fa:x(i)ta] which meaning "ring dove". It was originally applied to the constellation Cygnus as al-Fākhtah, but later transferred to this star.[13][14][15][16] The etymology of its name hadāri (unknown meaning)[17] has also been suggested.

In Chinese, 丈人 (Zhàng Rén), meaning Grandfather, refers to an asterism consisting of α Columbae and ε Columbae.[18] Consequently, α Columbae itself is known as 丈人一 (Zhàng Rén yī, English: the First Star of Grandfather.).[19] From this Chinese name, the name Chang Jin was appeared[20]

References[edit]

  1. ^ a b c d e f van Leeuwen, F. (November 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 
  2. ^ a b c d Cousins, A. W. J. (1972), "UBV Photometry of Some Very Bright Stars", Monthly Notes of the Astronomical Society, Southern Africa 31: 69, Bibcode:1972MNSSA..31...69C 
  3. ^ a b Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1982MSS...C03....0H 
  4. ^ HR 1956, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line April 21, 2009.
  5. ^ Wilson, R. E. (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institute of Washington D.C. Bibcode:1953GCRV..C......0W. 
  6. ^ a b Jim Kaler: Phact - STARS. Accessed on line April 21, 2009.
  7. ^ a b c Meilland, A.; Stee, Ph.; Chesneau, O.; Jones, C. (October 2009), "VLTI/MIDI observations of 7 classical Be stars", Astronomy and Astrophysics 505 (2): 687–693, arXiv:0908.1239, Bibcode:2009A&A...505..687M, doi:10.1051/0004-6361/200911960 
  8. ^ a b c Oudmaijer, R. D. et al. (October 2008), "Sub-milliarcsecond precision spectro-astrometry of Be stars", Astronomy and Astrophysics 489 (2): 627–631, arXiv:0807.3673, Bibcode:2008A&A...489..627O, doi:10.1051/0004-6361:20079117 
  9. ^ * alf Col -- Be Star, database entry, SIMBAD. Accessed on line April 21, 2009.
  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. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. 
  11. ^ CCDM J05396-3404, database entry, J. Dommanget and O. Nys (2002) Catalogue of the Components of Double and Multiple Stars, Accessed on line April 21, 2009.
  12. ^ a b Note of HR 1956, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line April 21, 2009.
  13. ^ Davis, Jr., G. A., (1971). Pronunciations, Derivations, and Meanings of a Selected List of Star Names (rep. ed.). Cambridge, MA: Sky Pub. Corp. p. 11. 
  14. ^ Kunitzsch, P., (1959). Arabische Sternnamen in Europa. Wiesbaden: Otto Harrassowitz. pp. 191–192. 
  15. ^ Laffitte, R., (2005). Héritages arabes: Des noms arabes pour les étoiles (2éme revue et corrigée ed.). Paris: Librairie Orientaliste Paul Geunthner / Les Cahiers de l'Orient. p. 223. 
  16. ^ Kunitzsch, P., & Smart, T., (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, MA: Sky Pub. p. 30. ISBN 978-1-931559-44-7. 
  17. ^ Allen, R. H., (1963). Star Names: Their Lore and Meaning (rep. ed.). New York, NY: Dover Publications Inc. p. 167. ISBN 0-486-21079-0. 
  18. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  19. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
  20. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Columbae