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). It is visible to the naked eye with an apparent visual magnitude of about 5.

A light curve for Chi Aquarii, plotted from Hipparcos data[9]
χ Aquarii
Location of χ Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 23h 16m 50.93916s[1]
Declination −07° 43′ 35.4023″[1]
Apparent magnitude (V) 4.75 - 5.10[2]
Characteristics
Spectral type M3 III[3]
U−B color index +1.60[4]
B−V color index +1.60[4]
Variable type SRb?[2]
Astrometry
Radial velocity (Rv)−13.72 ± 0.86[5] km/s
Proper motion (μ) RA: −19.18[1] mas/yr
Dec.: −14.10[1] mas/yr
Parallax (π)5.32 ± 0.37 mas[1]
Distance610 ± 40 ly
(190 ± 10 pc)
Absolute magnitude (MV)−1.43[6]
Details
Radius142[7] R☉
Luminosity2,598[7] L☉
Surface gravity (log g)0.128[7] cgs
Temperature3,456[7] K
Other designations
χ Aqr, 92 Aquarii, BD−08 6076, HD 219576, HIP 114939, HR 8850, SAO 146612.[8]
Database references
SIMBADdata

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,[10] which, at its estimated distance, equates to a physical radius of about 137 times the radius of the Sun.[lower-alpha 1] It is classified as a semi-regular variable star and its brightness varies by an amplitude of 0.0636 in magnitude.[11] The identified pulsation periods are 32.3, 38.5, and 44.9 days.[12]

Notes
  1. The radius (R*) is given by [13]

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. Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)", VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S, 1, Bibcode:2009yCat....102025S.
  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, Bibcode:1973MNRAS.162...11C, doi:10.1093/mnras/162.1.11.
  4. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  5. Famaey, B.; et al. (May 2009), "Spectroscopic binaries among Hipparcos M giants. I. Data, orbits, and intrinsic variations", Astronomy and Astrophysics, 498 (2): 627–640, arXiv:0901.0934, Bibcode:2009A&A...498..627F, doi:10.1051/0004-6361/200810698, S2CID 18739721.
  6. 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.
  7. McDonald, I.; Zijlstra, A. A.; Watson, R. A. (15 June 2017), "Fundamental parameters and infrared excesses of Tycho–Gaia stars", Monthly Notices of the Royal Astronomical Society, 471 (1): 770–791, arXiv:1706.02208, Bibcode:2017MNRAS.471..770M, doi:10.1093/mnras/stx1433, eISSN 1365-2966, ISSN 0035-8711.
  8. "chi Aqr -- Semi-regular pulsating Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-05.
  9. "/ftp/cats/more/HIP/cdroms/cats", Centre de Données astronomiques de Strasbourg, Strasbourg astronomical Data Center, retrieved 15 October 2022.
  10. Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
  11. 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, arXiv:astro-ph/0112194, Bibcode:2002MNRAS.331...45K, doi:10.1046/j.1365-8711.2002.05150.x, S2CID 10505995.
  12. 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, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x, S2CID 15358380.
  13. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1
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