Phi Aquarii

Phi Aquarii, Latinized from φ Aquarii, is the Bayer designation for a binary star[8] system in the equatorial constellation of Aquarius. It is visible to the naked eye with a combined apparent visual magnitude of +4.223.[2] Parallax measurements indicate its estimated distance from Earth is roughly 222 light-years (68 parsecs),[1] and it is drifting further away with a radial velocity of +2.5 km/s.[4] The proximity of this star to the ecliptic means it is subject to lunar occultations.[9]

Phi Aquarii
Location of φ Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  23h 14m 19.35965s[1]
Declination –06° 02′ 56.3986″[1]
Apparent magnitude (V) +4.223[2]
Characteristics
Spectral type M1.5 III[3]
U−B color index +1.897[2]
B−V color index +1.563[2]
Astrometry
Radial velocity (Rv)+2.48±0.32[4] km/s
Proper motion (μ) RA: +35.391[1] mas/yr
Dec.: –196.862[1] mas/yr
Parallax (π)14.6670 ± 0.4099[1] mas
Distance222 ± 6 ly
(68 ± 2 pc)
Absolute magnitude (MV)0.30±0.120[5]
Details
Mass1.00±0.03[6] M☉
Radius34.77+1.83
−2.04[6] R☉
Luminosity207.7±25.2[6] L☉
Surface gravity (log g)1.5[4] cgs
Temperature3715±48[6] K
Rotational velocity (v sin i)6.7[4] km/s
Age10.97±0.83[6] Gyr
Other designations
φ Aqr, 90 Aquarii, BD–06°6170, FK5 1607, HD 219215, HIP 114724, HR 8834, SAO 146585[7]
Database references
SIMBADdata

This is a spectroscopic binary star system with an estimated period of 2,500 days.[10] The primary component is a red giant star with a stellar classification of M1.5 III.[3] The outer envelope of this evolved star has expanded to 35 times the size of the Sun. The star has the same mass as the Sun.[6] It is radiating 208 times the luminosity of the Sun at an effective temperature of 3,715 K,[6] giving it the reddish hue of an M-type star.[11]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards, 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G.
  3. Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333.
  4. 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.
  5. Park, Sunkyung; et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal, 146 (4): 73, arXiv:1307.0592, Bibcode:2013AJ....146...73P, doi:10.1088/0004-6256/146/4/73.
  6. Baines, Ellyn K.; et al. (2018). "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 155. 30. arXiv:1712.08109. Bibcode:2018AJ....155...30B. doi:10.3847/1538-3881/aa9d8b.
  7. "* phi Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-05.
  8. 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.
  9. White, Nathaniel M.; Feierman, Barry H. (September 1987), "A Catalog of Stellar Angular Diameters Measured by Lunar Occultation", Astronomical Journal, 94: 751, Bibcode:1987AJ.....94..751W, doi:10.1086/114513.
  10. 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.
  11. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-07-02.
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