第二型造父變星

第二型造父變星（Type II Cepheid）是變星的一種，它的脈動通常介於1至50天之間。第二型造父變星通常是第二星族星，因此是老年、通常貧金屬、低質量的恆星。 過去 (歷史上) 常常以室女座W型變星取代第二型造父變星的名稱，但現在依據周期分為幾個子群，室女座W型變星只是其中的一種。週期在1-4天的屬於BL Her子群、10-20天的屬於W Vir子群、週期超過20天的屬於RV Tau子群。 第二型造父變星遵守著周光關係，因此是重要的標準燭光，但是它們比同週期的經典造父變星暗了1.6星等。第二型造父變星常用來測量和建立銀河中心、球狀星團和星系的距離。 第二型造父變星的週期越長，光度也越亮，曾經用來測量在本星系群之外的NGC 5128和NGC 4258的距離。 Wallerstein, George. The Cepheids of Population II and Related Stars. The Publications of the Astronomical Society of the Pacific. 2002, 114 (797): 689. Bibcode:2002PASP..114..689W. doi:10.1086/341698.  Soszyński, I.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Wyrzykowski, Ł.; Szewczyk, O.; Ulaczyk, K.; Poleski, R. 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. 2008, 58: 293. Bibcode:2008AcA....58..293S.  Cepheid Variables. Weekly Topic. Caglow. [30 January 2012]. （原始内容存档于2018-09-09）.  Kubiak, M.; Udalski, A. The Optical Gravitational Lensing Experiment. Population II Cepheids in the Galactic Bulge. Acta Astronomica. 2003, 53: 117. Bibcode:2003AcA....53..117K. arXiv:astro-ph/0306567 .  Matsunaga, Noriyuki; Fukushi, Hinako; Nakada, Yoshikazu; Tanabé, Toshihiko; Feast, Michael W.; Menzies, John W.; Ita, Yoshifusa; Nishiyama, Shogo; Baba, Daisuke. The period-luminosity relation for type II Cepheids in globular clusters. Monthly Notices of the Royal Astronomical Society. 2006, 370 (4): 1979. Bibcode:2006MNRAS.370.1979M. arXiv:astro-ph/0606609 . doi:10.1111/j.1365-2966.2006.10620.x.  Feast, Michael W.; Laney, Clifton D.; Kinman, Thomas D.; van Leeuwen, Floor; Whitelock, Patricia A. The luminosities and distance scales of type II Cepheid and RR Lyrae variables. Monthly Notices of the Royal Astronomical Society. 2008, 386 (4): 2115. Bibcode:2008MNRAS.386.2115F. doi:10.1111/j.1365-2966.2008.13181.x.  Majaess, Daniel J.; Turner, David G.; Lane, David J. Characteristics of the Galaxy according to Cepheids. Monthly Notices of the Royal Astronomical Society. 2009, 398: 4206. Bibcode:2009MNRAS.398..263M. arXiv:0903.4206 . doi:10.1111/j.1365-2966.2009.15096.x.  Majaess, D.; Turner, D.; Lane, D. Type II Cepheids as Extragalactic Distance Candles. Acta Astronomica. 2009, 59: 403. Bibcode:2009AcA....59..403M.  Majaess, D. J. RR Lyrae and Type II Cepheid Variables Adhere to a Common Distance Relation. The Journal of the American Association of Variable Star Observers. 2010, 38: 100. Bibcode:2010JAVSO..38..100M.  Matsunaga, Noriyuki; Feast, Michael W.; Menzies, John W. Period-luminosity relations for type II Cepheids and their application. Monthly Notices of the Royal Astronomical Society. 2009, 397 (2): 933. Bibcode:2009MNRAS.397..933M. doi:10.1111/j.1365-2966.2009.14992.x.  Macri, L. M.; Stanek, K. Z.; Bersier, D.; Greenhill, L. J.; Reid, M. J. A New Cepheid Distance to the Maser-Host Galaxy NGC 4258 and Its Implications for the Hubble Constant. The Astrophysical Journal. 2006, 652 (2): 1133. Bibcode:2006ApJ...652.1133M. arXiv:astro-ph/0608211 . doi:10.1086/508530.  Ferrarese, Laura; Mould, Jeremy R.; Stetson, Peter B.; Tonry, John L.; Blakeslee, John P.; Ajhar, Edward A. The Discovery of Cepheids and a Distance to NGC 5128. The Astrophysical Journal. 2007, 654: 186. Bibcode:2007ApJ...654..186F. arXiv:astro-ph/0605707 . doi:10.1086/506612.  Majaess, D. The Cepheids of Centaurus A (NGC 5128) and Implications for H0. Acta Astronomica. 2010, 60: 121. Bibcode:2010AcA....60..121M.