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[1][2]。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[1]。
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,但現在依據週期分為幾個子群,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[1][2]。
第二型造父變星遵守着周光關係,因此是重要的標準燭光[2],但是它們比同週期的經典造父變星暗了1.6星等[3]。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[4][5][6][7][8][9][10]。
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[8][11][12][13]。
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.
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, 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.
Majaess, D. The Cepheids of Centaurus A (NGC 5128) and Implications for H0. Acta Astronomica. 2010, 60: 121. Bibcode:2010AcA....60..121M.