Type II Cepheid

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Type II Cepheids are variable stars which pulsate with periods typically between 1 and 50 days.[1][2] Like all Cepheid variables, Type IIs exhibit a relationship between the star's luminosity and pulsation period[3][4] Type II Cepheids are population II stars and are thus old, typically metal-poor, and low mass objects.[1]

Historically Type II Cepheids were called W Virginis variables, but are now divided into three subclasses based on the length of their period. Stars with periods between 1 and 4 days are of the BL Herculis subclass, 10–20 days belong to the W Virginis subclass, and stars with periods greater than 20 days belong to the RV Tauri subclass.[1][2]

Type II Cepheids are important standard candles since they obey a period-luminosity relationship,[2] although they are fainter than their classical Cepheid counterparts for a given period by about 1.6 magnitudes.[5] Cepheid variables are used to establish the distance to the Galactic center, globular clusters, and galaxies.[6][7][8][9][10][11][12]

Longer period Type II Cepheids, which are more luminous, have been detected beyond the Local Group in the galaxies NGC 5128 and NGC 4258.[10][13][14][15]

Designation (name) Constellation Discovery Apparent magnitude (Maximum)[16] Apparent magnitude (Minimum)[17] Range of magnitude Period Spectral class Subtype Comment
RU Camelopardalis Camelopardalis   !B9979081359383 8m.1 !B9977186385434 9m.79 !B9995237658210 1.61 !B9969089575466 22 d C0,1-C3,2e(K0-R0) W Virginis variable (CW) Carbon-rich[18]
Kappa Pavonis Pavo   !B9986364626260 3m.91 !B9984355594534 4m.78 !D0001392620673 0.87 !B9977923598535 09.09423 d F5-G5I-II W Virginis variable (CW) brightest member
RT Trianguli Australis Triangulum Australe   !B9977561039033 9m.43 !B9976795749888 10m.18 !D0010498221244 0.35 !B9993341662583 1.9461124 d F8:(R)-G2I-II BL Herculis variable (CWB) carbon-rich[19]
AL Virginis Virgo   !B9977917255864 9m.10 !B9977054470787 9m.92 !D0001984509387 0.82 !B9976672252358 10.3065 d F0-F8 W Virginis variable (CW)  
W Virginis Virgo   !B9977529276169 9m.46 !B9976250942454 10m.75 !D0001392620673 0.87 !B9971508206755 17.2736 d F0Ib-G0Ib W Virginis variable (CW) prototype


  1. ^ a b c Wallerstein, George (2002). "The Cepheids of Population II and Related Stars". The Publications of the Astronomical Society of the Pacific 114 (797): 689. Bibcode:2002PASP..114..689W. doi:10.1086/341698. 
  2. ^ a b c Soszyński, I.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Wyrzykowski, Ł.; Szewczyk, O.; Ulaczyk, K.; Poleski, R. (2008). "The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. II.Type II Cepheids and Anomalous Cepheids in the Large Magellanic Cloud". Acta Astronomica 58: 293. arXiv:0811.3636. Bibcode:2008AcA....58..293S. 
  3. ^ Udalski, A.; Soszynski, I.; Szymanski, M.; Kubiak, M.; Pietrzynski, G.; Wozniak, P.; Zebrun, K. (1999). "The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. IV. Catalog of Cepheids from the Large Magellanic Cloud". Acta Astronomica 49: 223. arXiv:astro-ph/9908317. Bibcode:1999AcA....49..223U. 
  4. ^ Soszynski, I.; Poleski, R.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Wyrzykowski, L.; Szewczyk, O.; Ulaczyk, K. (2008). "The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. I. Classical Cepheids in the Large Magellanic Cloud". Acta Astronomica 58: 163. arXiv:0808.2210. Bibcode:2008AcA....58..163S. 
  5. ^ "Cepheid Variables". Weekly Topic. Caglow. Retrieved 30 January 2012. 
  6. ^ Kubiak, M.; Udalski, A. (2003). "The Optical Gravitational Lensing Experiment. Population II Cepheids in the Galactic Bulge". Acta Astronomica 53: 117. arXiv:astro-ph/0306567. Bibcode:2003AcA....53..117K. 
  7. ^ Matsunaga, Noriyuki; Fukushi, Hinako; Nakada, Yoshikazu; Tanabé, Toshihiko; Feast, Michael W.; Menzies, John W.; Ita, Yoshifusa; Nishiyama, Shogo et al. (2006). "The period-luminosity relation for type II Cepheids in globular clusters". Monthly Notices of the Royal Astronomical Society 370 (4): 1979. arXiv:astro-ph/0606609. Bibcode:2006MNRAS.370.1979M. doi:10.1111/j.1365-2966.2006.10620.x. 
  8. ^ Feast, Michael W.; Laney, Clifton D.; Kinman, Thomas D.; van Leeuwen, Floor; Whitelock, Patricia A. (2008). "The luminosities and distance scales of type II Cepheid and RR Lyrae variables". Monthly Notices of the Royal Astronomical Society 386 (4): 2115. arXiv:0803.0466. Bibcode:2008MNRAS.386.2115F. doi:10.1111/j.1365-2966.2008.13181.x. 
  9. ^ Majaess, Daniel J.; Turner, David G.; Lane, David J. (2009). "Characteristics of the Galaxy according to Cepheids". Monthly Notices of the Royal Astronomical Society 398: 4206. arXiv:0903.4206. Bibcode:2009MNRAS.398..263M. doi:10.1111/j.1365-2966.2009.15096.x. 
  10. ^ a b Majaess, D.; Turner, D.; Lane, D. (2009). "Type II Cepheids as Extragalactic Distance Candles". Acta Astronomica 59: 403. arXiv:0909.0181. Bibcode:2009AcA....59..403M. 
  11. ^ Majaess, D. J. (2010). "RR Lyrae and Type II Cepheid Variables Adhere to a Common Distance Relation". The Journal of the American Association of Variable Star Observers 38: 100. arXiv:0912.2928. Bibcode:2010JAVSO..38..100M. 
  12. ^ Matsunaga, Noriyuki; Feast, Michael W.; Menzies, John W. (2009). "Period-luminosity relations for type II Cepheids and their application". Monthly Notices of the Royal Astronomical Society 397 (2): 933. arXiv:0904.4701. Bibcode:2009MNRAS.397..933M. doi:10.1111/j.1365-2966.2009.14992.x. 
  13. ^ Macri, L. M.; Stanek, K. Z.; Bersier, D.; Greenhill, L. J.; Reid, M. J. (2006). "A New Cepheid Distance to the Maser-Host Galaxy NGC 4258 and Its Implications for the Hubble Constant". The Astrophysical Journal 652 (2): 1133. arXiv:astro-ph/0608211. Bibcode:2006ApJ...652.1133M. doi:10.1086/508530. 
  14. ^ Ferrarese, Laura; Mould, Jeremy R.; Stetson, Peter B.; Tonry, John L.; Blakeslee, John P.; Ajhar, Edward A. (2007). "The Discovery of Cepheids and a Distance to NGC 5128". The Astrophysical Journal 654: 186. arXiv:astro-ph/0605707. Bibcode:2007ApJ...654..186F. doi:10.1086/506612. 
  15. ^ Majaess, D. (2010). "The Cepheids of Centaurus A (NGC 5128) and Implications for H0". Acta Astronomica 60: 121. arXiv:1006.2458. Bibcode:2010AcA....60..121M. 
  16. ^ (visual magnitude, unless marked (B) (= blue) or (p) (= photographic))
  17. ^ (visual magnitude, unless marked (B) (= blue) or (p) (= photographic))
  18. ^ Kipper, Tõnu; Klochkova, Valentina G. (2007). "Optical Spectroscopy of RU Cam, a Pulsating Carbon Star". Baltic Astronomy 16: 383–96. arXiv:0706.2969. Bibcode:2007BaltA..16..383K. 
  19. ^ Wallerstein, George; Matt, Sean; Gonzalez, Guillermo (2000), "The Carbon Cepheid RT Trianguli Australis: Additional Evidence of Triple-α and CNO Cycling", Monthly Notices of the Royal Astronomical Society 311 (2): 414–22, Bibcode:2000MNRAS.311..414W, doi:10.1046/j.1365-8711.2000.03064.x 

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