Alpha Columbae

Alpha Columbae or α Columbae, officially named Phact (/ˈfækt/),^[12][13] 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]

Alpha Columbae

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	B9Ve[3] or B7 IV[4]
U−B color index	−0.44[2]
B−V color index	−0.125[2]
R−I color index	−0.09[5]
Astrometry
Radial velocity (Rv)	+35.0[6] km/s
Proper motion (μ)	RA: −1.58[1] mas/yr Dec.: −24.82[1] mas/yr
Parallax (π)	12.48 ± 0.36 mas[1]
Distance	261 ± 8 ly (80 ± 2 pc)
Absolute magnitude (MV)	−1.87[7]
Details
Mass	4.5[8] M☉
Radius	7±0.14[9] R☉
Luminosity (bolometric)	1,000[8] L☉
Surface gravity (log g)	3.5±0.04[9] cgs
Temperature	12,200±122[9] K
Rotational velocity (v sin i)	176[10] km/s
Age	93[3] Myr
Other designations
Alpha Col, α Col, NSV 2549, CD−34 2375, CPD−34 703, FK5 215, GC 7078, HD 37795, HIP 26634, HR 1956, SAO 196059, PPM 281732, CCDM  J05396−3404 A[11]
Database references
SIMBAD	data

Nomenclature

α Columbae, Latinized to Alpha Columbae, is the star's Bayer designation.

The traditional name of Phact (also rendered Phad, Phaet, Phakt)^[14] derives from the Arabic فاختة fākhitah 'ring dove'. It was originally applied to the constellation Cygnus and later transferred to this star.^{[15][16][17][18]} The etymology of its name hadāri (unknown meaning)^[19] has also been suggested. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[20] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016^[21] 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.^[22] Consequently, α Columbae itself is known as 丈人一 (Zhàng Rén yī, English: the First Star of Grandfather.).^[23] From this Chinese name, the name Chang Jin has appeared^[24]

Properties

This is believed to be a solitary star,^[10][25] although it has a faint optical companion at an angular separation of 13.5 arcseconds, making it a double star.^[26] The stellar classification of Alpha Columbae is B9Ve,^[3] matching a B-type main-sequence 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.^[14] 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.^[10] It is a suspected Gamma Cassiopeiae type (GCAS) variable star, with its apparent magnitude varying from 2.62^m to 2.66^m.

References

1. 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, S2CID 18759600
2. 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
3. Levenhagen, R. S.; Leister, N. V. (2006), "Spectroscopic analysis of southern B and Be stars", Monthly Notices of the Royal Astronomical Society, 371 (1): 252–262, arXiv:astro-ph/0606149, Bibcode:2006MNRAS.371..252L, doi:10.1111/j.1365-2966.2006.10655.x, S2CID 16492030.
4. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1982mcts.book.....H
5. 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.
6. Wilson, R. E. (1953). "General Catalogue of Stellar Radial Velocities". Carnegie Institute Washington D.C. Publication. Carnegie Institute of Washington D.C. Bibcode:1953GCRV..C......0W.
7. 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.
8. Jim Kaler: Phact - STARS Archived 2008-07-04 at the Wayback Machine. Accessed on line April 21, 2009.
9. Arcos, C; Kanaan, S; Chávez, J; Vanzi, L; Araya, I; Curé, M (2018-01-03). "Stellar parameters and H α line profile variability of Be stars in the BeSOS survey". Monthly Notices of the Royal Astronomical Society. 474 (4): 5287–5299. arXiv:1711.08675. doi:10.1093/mnras/stx3075. ISSN 0035-8711.
10. 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, S2CID 10317142
11. "alf Col". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved April 21, 2009.
12. 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.
13. "IAU Catalog of Star Names". Retrieved 28 July 2016.
14. 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.
15. 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.
16. Kunitzsch, P. (1959). Arabische Sternnamen in Europa. Wiesbaden: Otto Harrassowitz. pp. 191–192.
17. Laffitte, R. (2005). Héritages arabes: Des noms arabes pour les étoiles (2^éme revue et corrigée ed.). Paris: Librairie Orientaliste Paul Geunthner / Les Cahiers de l'Orient. p. 223.
18. 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.
19. 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.
20. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
21. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
22. (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.
23. (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.
24. Richard Hinckley Allen: Star Names — Their Lore and Meaning: Columbae
25. 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. S2CID 14878976.
26. 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.