Epsilon Aquarii

Epsilon Aquarii, Latinized from ε Aquarii, is a single[11] star in the equatorial zodiac constellation of Aquarius, located near the western constellation border with Capricornus. It has the proper name Albali /ælˈbeɪli/, now formally recognized by the IAU.[12][13] This is a white-hued star that is visible to the naked eye with an apparent visual magnitude of 3.77.[2] Based upon parallax measurements taken during the Hipparcos mission, it is located at a distance of approximately 208 light-years (64 pc) from the Sun[1] with an absolute magnitude of −0.46.[7] The star is drifting closer with a radial velocity of −15 km/s.[6]

Epsilon Aquarii
Location of ε Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  20h 47m 40.55260s[1]
Declination −09° 29′ 44.7877″[1]
Apparent magnitude (V) 3.77[2]
Characteristics
Evolutionary stage Main sequence[3]
Spectral type A1 V[2]
U−B color index +0.029[4]
B−V color index –0.001[4]
Variable type Constant[5]
Astrometry
Radial velocity (Rv)−15.3±0.6[6] km/s
Proper motion (μ) RA: +33.98[1] mas/yr
Dec.: -34.77[1] mas/yr
Parallax (π)15.70 ± 0.21[1] mas
Distance208 ± 3 ly
(63.7 ± 0.9 pc)
Absolute magnitude (MV)−0.46[7]
Details
Mass2.98±0.03[3] M☉
Radius2.5[8] R☉
Luminosity138.0+5.4
−5.2[3] L☉
Surface gravity (log g)3.66±0.14[9] cgs
Temperature9,622±327[9] K
Metallicity [Fe/H]−0.08±0.35[5] dex
Rotational velocity (v sin i)118.0±5.9[7] km/s
Age388[9] Myr
Other designations
Albali, ε Aqr, 2 Aquarii, BD–10°5506, FK5 781, HD 198001, HIP 102618, HR 7950, SAO 144810[10]
Database references
SIMBADdata

This object is an A-type main-sequence star with a stellar classification of A1 V.[2] It is an estimated 388[9] million years old with a high rate of spin, showing a projected rotational velocity of around 118 km/s.[7] The elemental abundances in the stellar atmosphere are close to solar, with pronounced underabundances of aluminium and strontium.[5] The star has three[3] times the mass of the Sun and about 2.5[8] times the Sun's radius. It is radiating 138[3] times the luminosity of the Sun from its photosphere at an effective temperature of 9,622 K.[9]

Nomenclature

ε Aquarii (Latinised to Epsilon Aquarii) is the star's Bayer designation.

It bore the traditional name, Albali, from the Arabic البالع (albāli‘), meaning "the swallower". (See also Albulaan.) Along with Mu Aquarii (Albulaan) and Nu Aquarii (also Albulaan), they were al Bulaʽ (البلع), meaning "the Swallower".[14][15] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[16] to catalogue and standardize proper names for stars. The WGSN approved the name Albali for this star on 12 September 2016, and it is now so included in the List of IAU-approved Star Names.[13]

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, it was designated Nir Saad Bula (نير سعد ألبلع nayyir sa'd al bulaʽ), which was translated into Latin as Lucida Fortunæ Dissipantis, meaning "the brightest of luck of the swallower".[17]

In Chinese, 女宿 (Nǚ Sù), meaning Girl (asterism), refers to an asterism consisting of Epsilon Aquarii, Mu Aquarii, 4 Aquarii, 5 Aquarii and 3 Aquarii.[18] Consequently, the Chinese name for Epsilon Aquarii itself is 女宿一 (Nǚ Sù yī, English: the First Star of Girl).[19]

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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.
  2. Levato, O. H. (August 1972), "Rotational Velocities and Spectral Types of Some A-Type Stars", Publications of the Astronomical Society of the Pacific, 84 (500): 584, Bibcode:1972PASP...84..584L, doi:10.1086/129336.
  3. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691.
  4. Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C.
  5. Kocer, D.; et al. (August 2003), "Elemental abundance analyses with DAO spectrograms. XXVII. The superficially normal stars theta And (A2 IV), epsilon Del (B6 III), epsilon Aqr (A1.5 V), and iota And (B9 V)", Astronomy and Astrophysics, 406: 975–980, Bibcode:2003A&A...406..975K, doi:10.1051/0004-6361:20030620.
  6. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  7. Ammler-von Eiff, M.; Reiners, A. (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724.
  8. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  9. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  10. "* eps Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-29.
  11. 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.
  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. Naming Stars, IAU.org, retrieved 16 December 2017.
  14. Davis Jr., G. A. (October 1944), "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names", Popular Astronomy, 52 (3): 12, Bibcode:1944PA.....52....8D.
  15. Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 53, ISBN 0-486-21079-0, retrieved 2010-12-12.
  16. IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  17. Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket", Monthly Notices of the Royal Astronomical Society, 55: 429, Bibcode:1895MNRAS..55..429K, doi:10.1093/mnras/55.8.429.
  18. (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.
  19. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived October 25, 2008, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
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