Lambda Aquarii

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Template:Short description

Lambda Aquarii
Template:Location mark
Location of λ Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 3.722[2] (3.57 to 3.80)[3]
Characteristics
Evolutionary stage AGB[4]
Spectral type M2.5 IIIa Fe–1[5]
U−B Template:Engvar +1.721[2]
B−V Template:Engvar +1.641[2]
Variable type Lb[3]
Astrometry
Radial velocity (Rv)Script error: No such module "val".[6] km/s
Proper motion (μ) RA: +14.964 mas/yr[1]
Dec.: +32.742 mas/yr[1]
Parallax (π)8.9360±0.2356 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)−1.5[7]
Details
MassScript error: No such module "val".[8] Template:Solar mass
RadiusScript error: No such module "val".[9] Template:Solar radius
Luminosity1,716[10] Template:Solar luminosity
Temperature3,702[10] K
Metallicity [Fe/H]−2.25[7] dex
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[11]
Database references
SIMBADdata

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Lambda Aquarii, informally known as Hydor (Template:IPAc-en),[12][13] is a variable star in the equatorial constellation of Aquarius. The name is Latinized from the Bayer designation λ Aquarii, and abbreviated Lambda Aqr or λ Aqr. The apparent visual magnitude of this star ranges from 3.57 down to 3.80,[3] which is bright enough to be visible with the naked eye. The star is eclipsed by the sun from about 1-4 March;[14] thus the star can be viewed the whole night, crossing the sky, in early September, in the current epoch. Lambda Aquarii is located at a distance of Script error: No such module "convert". from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −10.5 km/s.[6]

This star lies just 0.39 degrees south of the ecliptic[15] and so is subject to lunar and planetary occultations.[16][17][18] On 16 April 2014, it was occulted by Venus as viewed from Australia, New Zealand and the West Pacific.[19]

Properties

File:LambdaAqrLightCurve.png
A visual band light curve for Lambda Aquarii, plotted from data published by Tabur et al. (2009).[20] The inset plot shows the same data folded with a period of 24.5 days, after a linear trend had been removed.

The stellar classification of Lambda Aquarii is M2.5 IIIa Fe–1,[5] indicating this is an aging red giant star with an underabundance of iron showing in its spectrum. This star is on the asymptotic giant branch and is generating energy through the nuclear fusion of hydrogen and helium along concentric shells surrounding an inert core of carbon and oxygen.[4] With 3.6[21] times the mass of the Sun, it has expanded to 100[9] times the Sun's radius.

Lambda Aquarii has a magnetic field with an effective strength measured at Script error: No such module "val"..[22] It is classified as slow irregular variable and pulsation periods of 24.5, 32.0, and 49.5 days have been identified.[20] On average, it is radiating nearly 1,600 times the luminosity of the Sun from the photosphere at an effective temperature of 3,702 K.[10]

Naming

Hydor is from Greek Ὕδωρ "water", a name given by Proclus, according to Richard Hinckley Allen. Another Greek name for the star is Ekkhysis, from εκχυσις "outpouring".[13]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Line of Ramparts, refers to an asterism consisting of λ Aquarii, κ Capricorni, ε Capricorni, γ Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium.[23] Consequently, λ Aquarii itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx.)[24]

References

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  1. ↑ a b c d e Template:Cite Gaia DR3
  2. ↑ a b c Script error: No such module "Citation/CS1".
  3. ↑ a b c Script error: No such module "Citation/CS1".
  4. ↑ a b Script error: No such module "Citation/CS1".
  5. ↑ a b Script error: No such module "Citation/CS1".
  6. ↑ a b Script error: No such module "Citation/CS1".
  7. ↑ a b Script error: No such module "Citation/CS1".
  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ a b Script error: No such module "Citation/CS1".
  10. ↑ a b c Script error: No such module "Citation/CS1". Lambda Aquarii's database entry at VizieR.
  11. ↑ Template:Cite simbad
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ a b Script error: No such module "citation/CS1".
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ John Pratt's stars re-publication by Dr J.P. Pratt (Doctor of Astronomy, University of Arizona) of sidereal coordinate data. Note: possibly a non-book published source.
  16. ↑ Script error: No such module "Citation/CS1".
  17. ↑ Script error: No such module "Citation/CS1".
  18. ↑ Script error: No such module "Citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ a b Script error: No such module "Citation/CS1".
  21. ↑ Script error: No such module "Citation/CS1". Isotopic abundances of Carbon and Oxygen in Oxygen-rich giant stars.
  22. ↑ Script error: No such module "Citation/CS1".
  23. ↑ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
  24. ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日 Template:Webarchive

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External links

Template:Stars of Aquarius

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