Type II Cepheid

Type II Cepheids are variable stars which pulsate with periods typically between 1 and 50 days.^[1][2] Type II Cepheids are population II stars and are thus old, typically metal-poor, low mass objects.^[1]

Type II Cepheids were historically called W Virginis variables, but are now divided into several subgroups by period. Stars with periods between 1 and 4 days are of the BL Her subclass, 10–20 days belong to the W Viriginis 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 relation,^[2] although they are fainter than their classical Cepheid counterparts at a given period by ~1.5 magnitudes. Type II Cepheids are used to establish the distance to the Galactic center, globular clusters, and galaxies.^{[3][4][5][6][7][8][9]}

Longer period Type II Cepheids, which are more luminous, have been detected beyond the Local Group in NGC 5128 and NGC 4258.^{[7][10][11][12]}

References

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. et al. (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. Bibcode 2008AcA....58..293S. 
3. ^ 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. 
4. ^ 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. 
5. ^ 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. Bibcode 2008MNRAS.386.2115F. doi:10.1111/j.1365-2966.2008.13181.x. 
6. ^ Majaess, Daniel J.; Turner, David G.; Lane, David J. (2009). "Characteristics of the Galaxy according to Cepheids". Monthly Notices of the Royal Astronomical Society 0903: 4206. arXiv:0903.4206. Bibcode 2009MNRAS.398..263M. doi:10.1111/j.1365-2966.2009.15096.x. 
7. ^ ^{a b} Majaess, D.; Turner, D.; Lane, D. (2009). "Type II Cepheids as Extragalactic Distance Candles". Acta Astronomica 59: 403. Bibcode 2009AcA....59..403M. 
8. ^ 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. Bibcode 2010JAVSO..38..100M. 
9. ^ 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. Bibcode 2009MNRAS.397..933M. doi:10.1111/j.1365-2966.2009.14992.x. 
10. ^ 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. 
11. ^ 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. 
12. ^ Majaess, D. (2010). "The Cepheids of Centaurus A (NGC 5128) and Implications for H0". Acta Astronomica 60: 121. Bibcode 2010AcA....60..121M.