WZ Cassiopeiae

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WZ Cassiopeiae
WZ Cassiopeiae.jpg
WZ Cassiopeiae in optical light
Observation data
Epoch J2000       Equinox J2000
Constellation Cassiopeia [1]
Right ascension 00h 01m 15.85680s [2]
Declination +60° 21′ 19.0259″ [2]
Apparent magnitude  (V)6.3 – 8.8 [3]
Characteristics
Evolutionary stage AGB [4]
Spectral type C-N7 III: C2 2 Li 10 [5]
U−B color index +4.29 [6]
B−V color index +2.835±0.040 [1]
Variable type SRb [3]
Astrometry
Radial velocity (Rv)−34.0±2 [7] km/s
Proper motion (μ)RA: +10.7693 [2] mas/yr
Dec.: −5.672 [2] mas/yr
Parallax (π)2.1227±0.0297  mas [2]
Distance 1,540 ± 20  ly
(471 ± 7  pc)
Details
Mass 5.2 [8]   M☉
Radius ~600 [9]   R☉
Luminosity 12,400 [10]   L☉
Surface gravity (log g)1.55 [8]   cgs
Temperature 3,095 [10]   K
Metallicity [Fe/H]−0.19 [8]   dex
Other designations
WZ Cas, BD+59°2810, HD 224855, HIP 99, SAO 21002 [11]
Database references
SIMBAD data

WZ Cassiopeiae (WZ Cas) is a deep red hued star in the northern constellation of Cassiopeia. It is a variable star with a magnitude that ranges from 6.3 down to 8.8, [3] placing it near the limit of naked eye visibility at peak magnitude. The estimated distance to this star, as determined from its annual parallax shift of 2.1  mas , [2] is about 1,540  light years. It is moving closer to the Earth with a heliocentric radial velocity of −34 km/s. [7]

A visual band light curve for WZ Cassiopeiae, adapted from Lebzelter et al. (2005) WZCasLightCurve.png
A visual band light curve for WZ Cassiopeiae, adapted from Lebzelter et al. (2005)

João de Moraes Pereira discovered that the star's brightness varies, in 1893. It was given its variable star designation in 1921. [12] This is a semiregular variable of subtype SRb [3] with periods of 186 and 366 days due to radial pulsations. [9]

This is an aging carbon star on the asymptotic giant branch. [9] Keenan (1993) assigned it a classification of C-N7 III: C2 2 Li 10, which indicates it is of the N star subtype in the revised Morgan–Keenan system, with a C2 strength index of 2 (a measure of the excess of carbon over oxygen) and an anomalously strong line of lithium at 6707  Å. [5] It is losing mass at the rate of 6.5×10−9 M☉ yr−1, which is on the low side for a star of this type. It has expanded to around 600 times the Sun's radius and is radiating 12,400 times the Sun's luminosity [10] from its photosphere at a relatively cool [13] effective temperature of 3,095 K. [10]

A magnitude 8.4 B-type visual companion, designated HD 224869, is located at an angular separation of 58″ . The difference in the radial velocities for the two stars – 20 km/s – is too large for them to be dynamically associated. [14]

References

  1. 1 2 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. 1 2 3 4 5 6 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. 1 2 3 4 Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID   125853869.
  4. ↑ Choplin, A.; Siess, L.; Goriely, S. (2024). "Proton ingestion in asymptotic giant branch stars as a possible explanation for J-type stars and AB2 grains". Astronomy and Astrophysics. 691: L7. arXiv: 2410.10300 . Bibcode:2024A&A...691L...7C. doi:10.1051/0004-6361/202451013.
  5. 1 2 Keenan, P. C. (1993). "Revised MK Spectral Classification of the Red Carbon Stars". Publications of the Astronomical Society of the Pacific . 105: 905. Bibcode:1993PASP..105..905K. doi: 10.1086/133252 .
  6. ↑ Mendoza v., Eugenio E.; Johnson, Harold L. (1965). "Multicolor Photometry of Carbon Stars". The Astrophysical Journal. 141: 161. Bibcode:1965ApJ...141..161M. doi: 10.1086/148097 .
  7. 1 2 Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington: 0. Bibcode:1953GCRV..C......0W.
  8. 1 2 3 Khalatyan, A.; Anders, F.; Chiappini, C.; Queiroz, A. B. A.; Nepal, S.; Dal Ponte, M.; Jordi, C.; Guiglion, G.; Valentini, M.; Torralba Elipe, G.; Steinmetz, M.; Pantaleoni-González, M.; Malhotra, S.; Jiménez-Arranz, Ó.; Enke, H.; Casamiquela, L.; Ardèvol, J. (2024). "Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost". Astronomy and Astrophysics. 691: A98. arXiv: 2407.06963 . Bibcode:2024A&A...691A..98K. doi:10.1051/0004-6361/202451427.
  9. 1 2 3 4 Lebzelter, T.; et al. (September 2005). "WZ Cas - variability on multiple time-scales". Astronomy and Astrophysics. 440 (1): 295–303. Bibcode:2005A&A...440..295L. doi: 10.1051/0004-6361:20053076 .
  10. 1 2 3 4 Bergeat, J; Knapik, A; Rutily, B (2002). "Carbon-rich giants in the HR diagram and their luminosity function". Astronomy & Astrophysics. 390 (3): 967–986. Bibcode:2002A&A...390..967B. doi: 10.1051/0004-6361:20020525 .
  11. ↑ "WZ Cas". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 27 August 2018.
  12. ↑ Hartwig; Muller (January 1921). "Benennung von neu entdeckten veränderlichen Sternen". Astronomische Nachrichten. 212 (19): 353–374. Bibcode:1921AN....212..353.. doi:10.1002/asna.19202121902 . Retrieved 23 December 2024.
  13. ↑ Alksnis, O.; Zacs, L. (May 1994). "The Violet Opacity in the Red Peculiar Stars (II). Spectral Analysis of the Cool Carbon Stars WZ CAS and V CYG". Astrophysics and Space Science. 215 (1): 73–82. Bibcode:1994Ap&SS.215...73A. doi:10.1007/BF00627461. S2CID   117515681.
  14. ↑ Herbig, George H. (June 1955). "HD 224869: an Optical Companion to WZ Cassiopeiae". Publications of the Astronomical Society of the Pacific. 67 (396): 181. Bibcode:1955PASP...67..181H. doi: 10.1086/126798 .
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