Zeta Cassiopeiae

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ζ Cassiopeiae
Cassiopeia constellation map.svg
Red circle.svg
Location of ζ Cassiopeiae (circled)
Observation data
Epoch J2000       Equinox J2000
Constellation Cassiopeia [1]
Right ascension 00h 36m 58.28419s [2]
Declination +53° 53′ 48.8673″ [2]
Apparent magnitude  (V)3.59 to 3.68 [3]
Characteristics
Spectral type B2IV [4]
U−B color index −0.89 [5]
B−V color index −0.19 [5]
Variable type SPB [3]
Astrometry
Radial velocity (Rv)2.0 [3] km/s
Proper motion (μ)RA: 17.38 mas/yr [2]
Dec.: −9.86 mas/yr [2]
Parallax (π)5.50±0.16  mas [2]
Distance 590 ± 20  ly
(182 ± 5  pc)
Absolute magnitude  (MV)−2.8 [6]
Details
Mass 8.96±0.13 [7]   M☉
Radius 6.1±0.3 [7]   R☉
Luminosity 7,200±900 [7]   L☉
Surface gravity (log g)3.81 [3]   cgs
Temperature 21,500±800 [8]   K
Metallicity [Fe/H]−0.23 [9]   dex
Rotation 5.37045 [3] days
Rotational velocity (v sin i)17±3 [3]  km/s
Age 22.9±1.2 [7]   Myr
Other designations
Fulu, ζ Cas, 17 Cassiopeiae, BD+53°105, FK5 17, GC 727, HD 3360, HIP 2920, HR 153, SAO 21566 [10]
Database references
SIMBAD data

Zeta Cassiopeiae is a variable star [10] in the constellation of Cassiopeia. It has the proper name Fulu, pronounced /ˈfuːluː/ ; [11] Zeta Cassiopeiae is its Bayer designation, which is Latinized from ζ Cassiopeiae and abbreviated Zeta Cas or ζ Cas. This star has a blue-white hue and is classified as a B-type subgiant with a variable apparent magnitude of about +3.6, making it visible to the naked eye. Based upon parallax measurements, it is approximately 590  light-years from the Sun.

Contents

Nomenclature

Cassiopeia starfield Cassiopeia starfield.jpg
Cassiopeia starfield

ζ Cassiopeiae (Latinised to Zeta Cassiopeiae) is the star's Bayer designation.

In Chinese astronomy, Zeta Cassiopeiae is called 附路, Pinyin: Fùlù, meaning Auxiliary Road, because this star is marking itself and standing alone in the Auxiliary Road asterism, Legs (mansion) (see Chinese constellation). [12] 附路 (Fùlù) was westernized into Foo Loo, but that name was also designated for Eta Cassiopeiae by R. H. Allen, with the meaning of "a by-path" [13] In 2016, the IAU organized a Working Group on Star Names (WGSN) [14] to catalog and standardize proper names for stars. The WGSN approved the name Fulu for Zeta Cassiopeiae on 30 June 2017 and it is now so included in the List of IAU-approved Star Names. [11]

Properties

At the age of 23 million years, [7] Zeta Cassiopeiae is a B2 subgiant, indicating that it has exhausted its core hydrogen and started to evolve away from the main sequence. It has an effective temperature of over 20,000 K, [8] with about nine times the mass of the sun, and is 7,200 times as luminous. [7] The star is rotating about its axis once every 5.4 days. [3]

Variability

A light curve for Zeta Cassiopeiae, plotted from TESS data ZetaCasLightCurve.png
A light curve for Zeta Cassiopeiae, plotted from TESS data

Zeta Cassiopeiae is a probable member of an unusual group of variable stars known as "Slowly Pulsating B" (SPB) stars. [16] It shows a pulsation frequency of 0.64 per day (or once every 1.56 days) and displays a weak magnetic field with a strength of roughly 3.35 × 10−2 T , which varies with a period of 5.37 days. [17] This likely matches the rotation rate of the star, which, when combined with the low projected rotational velocity, indicates the star may be seen nearly pole-on. Zeta Cassiopeiae is a candidate magnetic Bp star that shows an overabundance of helium. The star contains a randomly oriented fossil magnetic field, which impacts the outflow of the stellar wind. Collisions between streams from this stellar wind creates a shock front, with cooling particles settling toward a co-rotating disk. [18]

References

  1. ↑ 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.{{cite journal}}: CS1 maint: postscript (link) XHIP record for this object at VizieR .
  2. 1 2 3 4 5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: 0708.1752 , Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID   18759600.
  3. 1 2 3 4 5 6 7 Neiner, C.; et al. (2003), "Discovery of a magnetic field in the Slowly Pulsating B star zeta Cassiopeiae" (PDF), Astronomy and Astrophysics, 406 (3): 1019, Bibcode:2003A&A...406.1019N, doi: 10.1051/0004-6361:20030742 .
  4. ↑ 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.
  5. 1 2 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  6. ↑ Jaschek, C.; Gomez, A. E. (1998), "The absolute magnitude of the early type MK standards from HIPPARCOS parallaxes", Astronomy and Astrophysics, 330: 619, Bibcode:1998A&A...330..619J.
  7. 1 2 3 4 5 6 Maestro, V.; et al. (2013), "Optical interferometry of early-type stars with PAVO@CHARA - I. Fundamental stellar properties", Monthly Notices of the Royal Astronomical Society, 434 (2): 1321, arXiv: 1306.5937 , Bibcode:2013MNRAS.434.1321M, doi: 10.1093/mnras/stt1092 , S2CID   2361434.
  8. 1 2 Gordon, Kathryn D.; et al. (March 2019), "Angular Sizes, Radii, and Effective Temperatures of B-type Stars from Optical Interferometry with the CHARA Array", The Astrophysical Journal, 873 (1): 91, Bibcode:2019ApJ...873...91G, doi: 10.3847/1538-4357/ab04b2 , S2CID   125181833.
  9. ↑ Gies, Douglas R.; Lambert, David L. (March 1992), "Carbon, nitrogen, and oxygen abundances in early B-type stars", Astrophysical Journal, Part 1, 387: 673–700, Bibcode:1992ApJ...387..673G, doi: 10.1086/171116 .
  10. 1 2 "Zet Cas", SIMBAD , Centre de données astronomiques de Strasbourg , retrieved 2025-09-23.
  11. 1 2 Naming Stars, IAU.org, archived from the original on 11 April 2020, retrieved 16 December 2017.
  12. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 9 日 Archived 2011-05-22 at the Wayback Machine
  13. ↑ Allen, Richard Hinckley, "Cassiopeia", Star Names — Their Lore and Meaning, retrieved 2025-09-25.
  14. ↑ IAU Working Group on Star Names (WGSN), archived from the original on 10 June 2016, retrieved 22 May 2016.
  15. ↑ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 24 December 2024.
  16. ↑ Neiner, C.; et al. (2003), "Discovery of a magnetic field in the Slowly Pulsating B star zeta Cassiopeiae", Astronomy and Astrophysics, 406 (3): 1019–1031, Bibcode:2003A&A...406.1019N, doi: 10.1051/0004-6361:20030742 .
  17. ↑ De Cat, P. (June 2007), "Observational Asteroseismology of slowly pulsating B stars", Communications in Asteroseismology, 150: 167–174, Bibcode:2007CoAst.150..167D, doi: 10.1553/cia150s167 .
  18. ↑ Smith, M. A.; Bohlender, D. A. (May 2007), "Variations of the ultraviolet resonance lines of the B2 IV-V star ζ Cassiopeiae", Astronomy and Astrophysics, 466 (2): 675–682, arXiv: astro-ph/0702461 , Bibcode:2007A&A...466..675S, doi:10.1051/0004-6361:20066639, S2CID   59063221.
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