Astronomy:Chi Aquarii

Chi Aquarii, Latinized from χ Aquarii, is the Bayer designation of a star in the equatorial constellation of Aquarius. The distance to this star, based upon parallax measurements with a 7% margin of error, is roughly 610 light-years (190 parsecs).[1] It is visible to the naked eye with an apparent visual magnitude of +5.06.[2]

This is a red giant star with a spectral classification of M3 III.[3] The interferometry-measured angular diameter of this star is 6.70 ± 0.15 mas,[4] which, at its estimated distance, equates to a physical radius of about 137 times the radius of the Sun.[5] It is classified as a semi-regular variable star and its brightness varies by an amplitude of 0.0636 in magnitude.[6] The identified pulsation periods are 32.3, 38.5, and 44.9 days.[7]

References

1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode2007A&A...474..653V.
2. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series 34: 1–49, Bibcode1978A&AS...34....1N.
3. Crampton, D.; Lloyd Evans, T. (1973), "Spectroscopic observations of M giant stars at the South Galactic Pole", Monthly Notices of the Royal Astronomical Society 162: 11–15, doi:10.1093/mnras/162.1.11, Bibcode1973MNRAS.162...11C.
4. Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431: 773–777, doi:10.1051/0004-6361:20042039, Bibcode2005A&A...431..773R.
5. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1 . The radius (R*) is given by:
\begin{align} 2\cdot R_* & = \frac{((190\cdot 6.70\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 274\cdot R_{\bigodot} \end{align}
6. Koen, Chris; Eyer, Laurent (March 2002), "New periodic variables from the Hipparcos epoch photometry", Monthly Notices of the Royal Astronomical Society 331 (1): 45–59, doi:10.1046/j.1365-8711.2002.05150.x, Bibcode2002MNRAS.331...45K.
7. Tabur, V. et al. (December 2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society 400 (4): 1945–1961, doi:10.1111/j.1365-2966.2009.15588.x, Bibcode2009MNRAS.400.1945T.

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