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  • 21 Aug, 2019

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91 Aquarii
91 Aquarii is the Flamsteed designation for a triple star system in the equatorial constellation of Aquarius. It also bears the Bayer designation Psi Aquarii (ψ Aqr, ψ Aquarii). It is visible to the naked eye with an apparent visual magnitude of +4.248. Parallax measurements yield an estimated distance of around 150 light-years (46 parsecs) from Earth. An extrasolar planet is known to orbit the main star.

Stellar system

91 Aquarii is a triple star system. The primary component, 91 Aqr A, is a giant star with a stellar classification of K1 III. This is an evolved star with 138% of the Sun's mass that has expanded to over 10 times the size of the Sun. It is radiating 54 times the Sun's luminosity from its outer envelope at an effective temperature of 4,730 K. This gives it the orange-hued glow of a K-type star.

The primary shares a common proper motion with two others stars, 91 Aqr B and C, suggesting that they are physically connected. The latter pair form a binary system located at an angular separation of 52 arcseconds from the primary. They are 10th magnitude stars separated by 0.3 arcseconds from each other.

Component Apparent magnitude (V) Spectral type
A 4.22 K0 III
B 9.62 K3 V
C 10.10

Because it lies near the same line of sight, the binary star system CCDM J23159-0905DE was listed to belong to the 91 Aquarii system according to the CCDM catalogue. However, it is listed as physically unconnected in the WDS catalogue and the pair have a different proper motion than 91 Aquarii. CCDM J23159-0905DE has two components, the 13th magnitude CCDM J23159-0905D 80.4 arcseconds from 91 Aquarii, and the 14th magnitude CCDM J23159-0905E 19.7 arcseconds from 91 Aquarii.

Planetary system

In 2003, the discovery of an extrasolar planet orbiting 91 Aquarii A was announced, but its confirmation was not formally published until 2013.

The 91 Aquarii planetary system
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b >3.2 MJ 0.70 181.4±0.1 0.027±0.026 — —

See also

References

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  2. ^ Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants.", Monthly Notices of the Royal Astronomical Society, 172 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
  3. ^ Baines, Ellyn K.; et al. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal, 155 (1), 30, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b, S2CID 119427037.
  4. ^ VizieR Detailed Page for HR 8841, retrieved 2009-11-28.
  5. ^ Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  6. ^ Liu, Y. J.; et al. (2007), "The abundances of nearby red clump giants", Monthly Notices of the Royal Astronomical Society, 382 (2): 553–66, Bibcode:2007MNRAS.382..553L, doi:10.1111/j.1365-2966.2007.11852.x.
  7. ^ 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, S2CID 14878976.
  8. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16.
  9. ^ Roell, T.; Neuhäuser, R.; Seifahrt, A.; Mugrauer, M. (June 2012), "Extrasolar planets in stellar multiple systems", Astronomy & Astrophysics, 542: A92, arXiv:1204.4833, Bibcode:2012A&A...542A..92R, doi:10.1051/0004-6361/201118051, S2CID 55755453
  10. ^ Buscombe, W. (1962), "Spectral classification of Southern fundamental stars", Mount Stromlo Observatory Mimeogram, 4: 1, Bibcode:1962MtSOM...4....1B.
  11. ^ "VizieR".
  12. ^ . January 31, 2009 https://web.archive.org/web/20090131051103/http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewframe4.html. Archived from the original on 2009-01-31. {{cite web}}: Missing or empty |title= (help)
  13. ^ Mitchell, D. S.; S. Frink; A. Quirrenbach; D. A. Fischer; G. W. Marcy; R. P. Butler (2004-01-05), "Four Substellar Companions Found Around K Giant Stars", Bulletin of the American Astronomical Society, 35#5; AAS 203rd Meeting; Session 17 Extra Solar Planets, 203: 17.03, Bibcode:2003AAS...203.1703M.
  14. ^ Mitchell, David S.; et al. (2013), "Precise radial velocities of giant stars. V. A brown dwarf and a planet orbiting the K giant stars τ Geminorum and 91 Aquarii", Astronomy and Astrophysics, 555, A87, arXiv:1305.5107, Bibcode:2013A&A...555A..87M, doi:10.1051/0004-6361/201321714, S2CID 32245543.


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