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Pi Aquarii

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π Aquarii
Location of π Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius[1]
Right ascension 22h 25m 16.623s[2]
Declination +01° 22′ 38.63″[2]
Apparent magnitude (V) 4.42 - 4.87[3]
Characteristics
Spectral type B1III-IVe[4]
U−B color index −0.98[5]
B−V color index −0.03[5]
Variable type γ Cas[3]
Astrometry
Radial velocity (Rv)+4.0[6] km/s
Proper motion (μ) RA: +17.518 mas/yr[2]
Dec.: +2.563 mas/yr[2]
Parallax (π)2.9761±0.1129 mas[2]
Distance1,100 ± 40 ly
(340 ± 10 pc)
Absolute magnitude (MV)−2.09[1]
Orbit[7]
Period (P)84.07±0.02 d
Semi-major axis (a)≥ 0.96 AU
Eccentricity (e)0.0 (fixed)
Periastron epoch (T)2,450,318.5±13.2 JD
Argument of periastron (ω)
(secondary)		0.0 (fixed)°
Semi-amplitude (K1)
(primary)		16.7±0.2 km/s
Semi-amplitude (K2)
(secondary)		101.4±0.2 km/s
Details
A
Mass10.7±0.7[8] M☉
Radius6.2[9] R☉
Luminosity7,302[10] L☉
Temperature27,094[9] K
Metallicity [Fe/H]−0.02[1] dex
Rotational velocity (v sin i)215[11] km/s
Age10.0±5.0[8] Myr
B
Mass0.5–0.8[12] M☉
Other designations
π Aqr, 52 Aquarii, BD+00 4872, FK5 1585, HD 212571, HIP 110672, HR 8539, SAO 127520[13]
Database references
SIMBADdata

Pi Aquarii is a binary star system in the equatorial constellation of Aquarius. Its name is a Bayer designation that is Latinized from π Aquarii, and abbreviated Pi Aqr or π Aqr. This system has a combined apparent visual magnitude of +4.57,[5] which is bright enough to be faintly visible to the naked eye. Based upon parallax measurements, it is located at a distance of approximately 1,100 light-years (340 parsecs) from the Sun.[2] It is drifting further away with a radial velocity of +4 km/s.[6]

Properties

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A white-light light curve for Pi Aquarii, adapted from Nazé et al. (2020)[14]

This is a binary star system with a period of 84.1 days in a circular orbit.[15][16] The primary component is a B1 giant or subgiant star.[4] This is a large star with nearly eleven[8] times the mass and over six times the radius of the Sun.[9] Pi Aquarii shines about 7,300[10] times as brightly as the Sun. This energy is being radiated from its outer atmosphere at an effective temperature of 27,094 K,[9] giving it the blue-hued glow of a B-type star.[17] It is spinning rapidly with a projected rotational velocity of 215 km/s.[11]

The secondary is likely a white dwarf star with a strong magnetic field and a mass of 0.5 to 0.8 M☉. It is an X-ray source which is probably coming from accretion onto this object, making this an intermediate polar system. The accretion rate is (4–7)×10−11 M☉·yr−1.[12]

Pi Aquarii is notable for having undergone a transition from a Be star (showing hydrogen emission lines) into an ordinary B-type star.[16] It is classified as a Gamma Cassiopeiae type[3] variable star and its brightness varies from magnitude +4.45 to +4.71; a range of 0.28. The dominant variability period, 83.8±0.8 days, is nearly the same as the orbital period.[16] Pi Aquarii has a reasonable chance of becoming a supernova some day.[15]

In culture

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Pi Aquarii was called Seat /ˈsiːæt/ by Grotius in the 17th century, but the name has rarely been used since.[15]

In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of π Aquarii, γ Aquarii, ζ Aquarii, η Aquarii.[18] Consequently, the Chinese name for π Aquarii itself is 墳墓四 (Fén Mù sì, English: the Fourth Star of Tomb.)[19]

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Wasat al Achbiya (وسط الأخبية - wasath al ahbiyah), which was translated into Latin as Media Tabernaculorum, meaning the middle of luck of the homes (tents).[20] This star, along with γ Aqr (Sadachbia), ζ Aqr (Sadaltager / Achr al Achbiya) and η Aqr (Hydria), were al Aḣbiyah (الأخبية), the Tent.[21][22][23]

References

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  1. ^ a b c 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.
  2. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b c "pi Aqr", General Catalogue of Variable Stars, Sternberg Astronomical Institute, retrieved 2012-07-03. Note: type = GCAS.
  4. ^ a b Slettebak, A. (1982), "Spectral types and rotational velocities of the brighter Be stars and A-F type shell stars", Astrophysical Journal Supplement Series, 50: 55, Bibcode:1982ApJS...50...55S, doi:10.1086/190820.
  5. ^ a b c 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.
  6. ^ a b Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astronomisches Rechen-Institut Heidelberg, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W.
  7. ^ Bjorkman, Karen S.; et al. (July 2002), "A Study of π Aquarii during a Quasi-normal Star Phase: Refined Fundamental Parameters and Evidence for Binarity", The Astrophysical Journal, 573 (2): 812–824, arXiv:astro-ph/0203357, Bibcode:2002ApJ...573..812B, doi:10.1086/340751, S2CID 14685744.
  8. ^ a b c Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  9. ^ a b c d Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601.
  10. ^ a b Hohle, M. M.; et al. (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.
  11. ^ a b Abt, Helmut A.; et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  12. ^ a b Huenemoerder, David P.; et al. (May 2024), "Chandra HETG X-Ray Spectra and Variability of π Aqr, a γ Cas-type Be Star", The Astrophysical Journal Letters, 966 (2): L23, arXiv:2404.16977, Bibcode:2024ApJ...966L..23H, doi:10.3847/2041-8213/ad4095, ISSN 2041-8205.
  13. ^ "pi. Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-03.
  14. ^ Nazé, Yaël; et al. (May 4, 2020), "Let there be more variability in two γ Cas stars", Monthly Notices of the Royal Astronomical Society, 494 (1): 958–974, arXiv:2002.12656, Bibcode:2020MNRAS.494..958N, doi:10.1093/mnras/staa617, retrieved 2 August 2022.
  15. ^ a b c Kaler, James, "Seat", Stars, retrieved 2017-08-18.
  16. ^ a b c Pollmann, Ernst (May 2012), "Period analysis of the Halpha line profile variation of the Be binary star pi Aqr", Information Bulletin on Variable Stars, 6023: 1, Bibcode:2012IBVS.6023....1P.
  17. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16
  18. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  19. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 16 日 Archived 2011-05-22 at the Wayback Machine
  20. ^ Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket", Monthly Notices of the Royal Astronomical Society, 55 (8): 429, Bibcode:1895MNRAS..55..429K, doi:10.1093/mnras/55.8.429.
  21. ^ Davis Jr., G. A. (October 1944), "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names", Popular Astronomy, 52 (3): 12, Bibcode:1944PA.....52....8D.
  22. ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 52, ISBN 0-486-21079-0, retrieved 2010-12-12. {{citation}}: ISBN / Date incompatibility (help)
  23. ^ γ Aqr as Aoul al Achbiya or Prima Tabernaculorum (the first of luck of the homes or tents), π Aqr as Wasat al Achbiya or Media Tabernaculorum (the middle of luck of the homes or tents) and ζ Aqr as Achr al Achbiya or Postrema Tabernaculorum (the end of luck of the homes or tents). η Aqr should be designated as al Achbiya consistently, but it was not designated as the Arabic name except the name Hydria (Greek) or Deli (Hebrew)
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