Rho Aquarii

Rho Aquarii, Latinized from ρ 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 an apparent visual magnitude of +5.34.[2] Based upon parallax measurements, this star is at a distance of roughly 870 light-years (270 parsecs) from Earth.[1] It is drifting closer with a radial velocity of –9 km/s.[4] The proximity of this star to the ecliptic means it is subject to lunar occultations.[10]

Rho Aquarii
Location of ρ Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 22h 20m 11.91830s[1]
Declination –07° 49′ 15.9742″[1]
Apparent magnitude (V) +5.34[2]
Characteristics
Spectral type B8 IIIp Mn:Hg:[3]
U−B color index –0.358[2]
B−V color index –0.057[2]
Astrometry
Radial velocity (Rv)–9[4] km/s
Proper motion (μ) RA: +13.201[1] mas/yr
Dec.: +0.030[1] mas/yr
Parallax (π)3.7483 ± 0.1608 mas[1]
Distance870 ± 40 ly
(270 ± 10 pc)
Absolute magnitude (MV)−1.78[5]
Orbit[6]
Period (P)220.41±0.10 d
Periastron epoch (T)2,418,548.7±7.4 JD
Semi-amplitude (K1)
(primary)		18.66±2.75 km/s
Details
A
Mass5.00±0.22[7] M☉
Luminosity1,035[7] L☉
Temperature12,593[8] K
Rotational velocity (v sin i)65[3] km/s
Other designations
ρ Aqr, 46 Aquarii, BD–08 5855, HD 211838, HIP 110273, HR 8512, SAO 146023[9]
Database references
SIMBADdata

This is a single-lined spectroscopic binary, with the presence of a companion being revealed by Doppler shifts in the spectrum.[8] An initial orbital solution for the data gives an orbital period of 220.4 days.[6] The primary is a giant star with a stellar classification of B8 IIIp Mn:Hg:.[3] It is a candidate mercury-manganese star, showing a surfeit of these elements in the spectrum.[8] With five times the Sun's mass, this star is radiating 1,035[7] times as much luminosity from its outer atmosphere at an effective temperature of 12,593 K.[8] This heat gives it the blue-white hue of a B-type star.[11] The companion may be a variable star.[12]

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. Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C.
  3. Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  4. Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  5. 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.
  6. Stickland, D. J.; Weatherby, J. (July 1984), "Radial velocities of northern mercury stars", Astronomy and Astrophysics, Supplemental Series, 57: 55–67, Bibcode:1984A&AS...57...55S.
  7. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
  8. Makaganiuk, V.; et al. (January 2011), "The search for magnetic fields in mercury-manganese stars", Astronomy and Astrophysics, 525: A97, arXiv:1010.3931, Bibcode:2011A&A...525A..97M, doi:10.1051/0004-6361/201015666, S2CID 118860674.
  9. "* rho Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-04.
  10. Hilaire, G. (March 1974), "Observations of occultations of stars by the moon", Astronomy and Astrophysics Supplement, 13: 395, Bibcode:1974A&AS...13..395H. See the SAO 146023 entry on p. 402.
  11. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2013-12-03, retrieved 2012-01-16
  12. Adelman, S. J.; Young, K. J. (January 2005), "uvby FCAPT photometry of the mCP stars HR 2258, MW Vul, and HR 9017 and the HgMn star 46 ρ Aqr", Astronomy and Astrophysics, 429: 317–322, Bibcode:2005A&A...429..317A, doi:10.1051/0004-6361:20041118.
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