Xi Aquarii is a binary star system in the equatorial constellation of Aquarius. Its name is a Bayer designation that is Latinized from ξ Aquarii, and abbreviated Xi Aqr or ξ Aqr. The system is visible to the naked eye as a point of light with an apparent visual magnitude of 4.7.[ The two components are designated Xi Aquarii A (also named Bunda][ It is drifting closer with a heliocentric radial velocity of –26 km/s.][ The position of this system near the ecliptic means it is subject to lunar occultation.][
]
Xi Aquarii is a single-lined spectroscopic binary system, which means that the presence of an unseen orbiting companion can be inferred from in the spectral . The two bodies orbit each other with a orbital period of 8,016 days (22 y) and an eccentricity of 0.54.[ The primary component, Xi Aquarii A, is an A-type main sequence star with a stellar classification of A7 V.][ It has about 1.7][ times the solar mass and is spinning rapidly with a projected rotational velocity of 170 km/s.][ The star is radiating 36][ times the luminosity of the Sun from its photosphere at an effective temperature of 8,140 K.][
]
The orbital data is consistent with the secondary component, Xi Aquarii B, being either a red dwarf or a white dwarf star.[
]
Nomenclature
ξ Aquarii (Latinised to Xi Aquarii) is the binary's Bayer designation. The designations of the two components as Xi Aquarii A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for Star system, and adopted by the International Astronomical Union (IAU).
Along with Beta Aquarii (Sadalsuud) it constituted the Persian lunar mansion Bunda.[ In 2016, the IAU organized a Working Group on Star Names (WGSN)]
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Thanih Saad al Saaoud (ثاني سعد السعود – ), which was translated into Latin as Secunda Fortunæ Fortunarum, meaning "the second of luck of lucks".[ This star, along with Beta Aquarii and 46 Capricorni, were (سعد السعود), "the Luck of Lucks".][
]
In Chinese, 天壘城 (Tiān Lěi Chéng), meaning Celestial Ramparts, refers to an asterism consisting of Xi Aquarii, 46 Capricorni, 47 Capricorni, Lambda Capricorni, 50 Capricorni, 18 Aquarii, 29 Capricorni, 9 Aquarii, 8 Aquarii, Nu Aquarii, 14 Aquarii, 17 Aquarii and 19 Aquarii.[ 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, .] Consequently, the Chinese name for Xi Aquarii itself is 天壘城一 (Tiān Lěi Chéng yī, ).[ 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.]
External links
