Astronomy:Pi Aquarii

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Short description: Star in the constellation Aquarius
π Aquarii
Aquarius constellation map.svg
Red circle.svg
Location of π Aquarii (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Aquarius
Right ascension  22h 25m 16.62285s[1]
Declination +01° 22′ 38.6346″[1]
Apparent magnitude (V) 4.42 - 4.87[2]
Characteristics
Spectral type B1III-IVe[3]
U−B color index −0.98[4]
B−V color index −0.03[4]
Variable type γ Cas[2]
Astrometry
Radial velocity (Rv)+4.0[5] km/s
Proper motion (μ) RA: +17.83[1] mas/yr
Dec.: +2.41[1] mas/yr
Parallax (π)4.17 ± 0.28[1] mas
Distance780 ± 50 ly
(240 ± 20 pc)
Absolute magnitude (MV)−2.09[6]
Orbit[7]
Period (P)84.07±0.02 d
Semi-major axis (a)≥ 0.96 astronomical unit|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[6] dex
Rotational velocity (v sin i)215[11] km/s
Age10.0±5.0[8] Myr
Other designations
π Aqr, 52 Aquarii, BD+00 4872, FK5 1585, HD 212571, HIP 110672, HR 8539, SAO 127520[12]
Database references
SIMBADdata

Pi Aquarii, Latinized from π Aquarii, is the Bayer designation for a binary star in the equatorial constellation of Aquarius. This system has an apparent visual magnitude of a mean apparent magnitude of +4.57.[4] Based upon parallax measurements, it is located at a distance of roughly 780 light-years (240 parsecs) from Earth.[1] It is drifting further away with a radial velocity of +4 km/s.[5]

A white-light light curve for Pi Aquarii, adapted from Nazé et al. (2020)[13]

This is a binary star system with an orbital period of 84.1 days.[14][15] The primary component is a B1 giant or subgiant star.[3] 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.[16] It is spinning rapidly with a projected rotational velocity of 215 km/s.[11] The nature of the secondary is unknown; some analyses have suggested it is an A- or F-type main-sequence star,[7] but the possibility of a white dwarf has not been ruled out.[17]

Pi Aquarii is notable for having undergone a transition from a Be star (showing hydrogen emission lines) into an ordinary B-type star.[15] It is classified as a Gamma Cassiopeiae type[2] 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.[15] Pi Aquarii has a reasonable chance of becoming a supernova some day.[14]

In culture

Pi Aquarii was called Seat /ˈsiːæt/ by Grotius in the 17th century, but the name has rarely been used since.[14]

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

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 "pi Aqr", General Catalogue of Variable Stars (Sternberg Astronomical Institute), http://www.sai.msu.su/gcvs/cgi-bin/ident.cgi?cat=HD++&num=212571, retrieved 2012-07-03.  Note: type = GCAS.
  3. ↑ 3.0 3.1 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. doi:10.1086/190820. Bibcode: 1982ApJS...50...55S. 
  4. ↑ 4.0 4.1 4.2 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. ↑ 5.0 5.1 Wielen, R. et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb (Astronomisches Rechen-Institut Heidelberg) 35 (35): 1, Bibcode: 1999VeARI..35....1W. 
  6. ↑ 6.0 6.1 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 "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. July 2002. doi:10.1086/340751. Bibcode: 2002ApJ...573..812B. 
  8. ↑ 8.0 8.1 8.2 Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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, doi:10.1111/j.1365-2966.2010.17434.x, Bibcode: 2011MNRAS.410..190T. 
  9. ↑ 9.0 9.1 9.2 9.3 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, doi:10.1093/mnras/189.3.601, Bibcode: 1979MNRAS.189..601U. 
  10. ↑ 10.0 10.1 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, doi:10.1002/asna.200911355, Bibcode: 2010AN....331..349H. 
  11. ↑ 11.0 11.1 Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, doi:10.1086/340590, Bibcode: 2002ApJ...573..359A. 
  12. ↑ "pi. Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=pi.+Aqr. 
  13. ↑ Nazé, Yaël; Pigulski, Andrzej; Rauw, Gregor; Smith, Myron A. (May 4, 2020). "Let there be more variability in two γ Cas stars". Monthly Notices of the Royal Astronomical Society 494 (1): 958–974. doi:10.1093/mnras/staa617. https://academic.oup.com/mnras/article/494/1/958/5780250. Retrieved 2 August 2022. 
  14. ↑ 14.0 14.1 14.2 Kaler, Jim. "Seat". http://stars.astro.illinois.edu/sow/seat.html. 
  15. ↑ 15.0 15.1 15.2 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. 
  16. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16 
  17. ↑ Tsujimoto, Masahiro; Hayashi, Takayuki; Morihana, Kumiko; Moritani, Yuki (2023). "X-ray and optical spectroscopic study of a γ Cassiopeiae analog source π Aquarii". Publications of the Astronomical Society of Japan 75 (1): 177–186. doi:10.1093/pasj/psac099. Bibcode: 2023PASJ...75..177T. 
  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
  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, doi:10.1093/mnras/55.8.429, Bibcode: 1895MNRAS..55..429K. 
  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, https://archive.org/details/starnamestheirlo00alle/page/52, retrieved 2010-12-12. 
  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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