Alpha Columbae
Alpha Columbae (α Columbae, abbreviated Alpha Col, α Col), officially named Phact /ˈfækt/,[11][12] is a third magnitude star in the southern constellation of Columba. 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]
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) | −1.87[6] |
Details | |
Mass | 4.5[7] M☉ |
Radius | 5.8[8] R☉ |
Luminosity (bolometric) | 1,000[7] L☉ |
Surface gravity (log g) | 3.73[8] cgs |
Temperature | 12,963[8] K |
Rotational velocity (v sin i) | 176[9] km/s |
Other designations | |
Database references | |
SIMBAD | data |
Nomenclature
Alpha Columbae is the star's Bayer designation.
The traditional name of Phact (also rendered Phad, Phaet, Phakt)[13] derives from the Arabic فاجتة fākhitah 'ring dove'. It was originally applied to the constellation Cygnus and later transferred to this star.[14][15][16][17] The etymology of its name hadāri (unknown meaning)[18] has also been suggested. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[19] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[20] included a table of the first two batches of names approved by the WGSN; which included Phact for this star.
In Chinese, 丈人 (Zhàng Rén), meaning Grandfather, refers to an asterism consisting of α Columbae and ε Columbae.[21] Consequently, α Columbae itself is known as 丈人一 (Zhàng Rén yī, English: the First Star of Grandfather.).[22] From this Chinese name, the name Chang Jin has appeared[23]
Properties
This is believed to be a solitary star,[9][24] although it has a faint optical companion at an angular separation of 13.5 arcseconds, making it a double star.[25] 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.[13] 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.[9] It is a suspected Gamma Cassiopeiae type (GCAS) variable star, with its apparent magnitude varying from 2.62m to 2.66m.
References
- 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
- Cousins, A. W. J. (1972), "UBV Photometry of Some Very Bright Stars", Monthly Notes of the Astronomical Society of Southern Africa, 31: 69, Bibcode:1972MNSSA..31...69C
- 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:1982mcts.book.....H
- 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.
- Wilson, R. E. (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institute of Washington D.C. Bibcode:1953GCRV..C......0W.
- 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.
- Jim Kaler: Phact - STARS Archived 2008-07-04 at the Wayback Machine. Accessed on line April 21, 2009.
- 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
- 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
- "alf Col". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved April 21, 2009.
- Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
- "IAU Catalog of Star Names". Retrieved 28 July 2016.
- 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.
- Davis, Jr. G. A. (1971). Pronunciations, Derivations, and Meanings of a Selected List of Star Names (Reprint ed.). Cambridge, MA: Sky Pub. Corp. p. 11.
- Kunitzsch, P. (1959). Arabische Sternnamen in Europa. Wiesbaden: Otto Harrassowitz. pp. 191–192.
- 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.
- 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.
- Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 167. ISBN 0-486-21079-0.
- "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
- (in 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.
- (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-30 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
- Richard Hinckley Allen: Star Names — Their Lore and Meaning: Columbae
- 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.
- 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.