Journal Article

Period–luminosity relations of type II Cepheids in the Magellanic Clouds

Noriyuki Matsunaga, Michael W. Feast and Igor Soszyński

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 413, issue 1, pages 223-234
Published in print May 2011 | ISSN: 0035-8711
Published online April 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.18126.x
Period–luminosity relations of type II Cepheids in the Magellanic Clouds

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Period–luminosity relations (PLRs) of type II Cepheids (T2Cs) in the Small Magellanic Cloud (SMC) are derived based on OGLE-III, IRSF/SIRIUS and other data, and these are compared with results for the Large Magellanic Cloud (LMC) and Galactic globular clusters. Evidence is found for a change of the PLR slopes from system to system. Treating the longer period T2Cs (W Vir stars) separately gives an SMC–LMC modulus difference of 0.39 ± 0.05 mag without any metallicity corrections being applied. This agrees well with the difference in moduli based on different distance indicators, in particular the PLRs of classical Cepheids. The shorter period T2Cs (BL Her stars) give a smaller SMC–LMC difference suggesting that their absolute magnitudes might be affected either by metallicity or by age effects. It is shown that the frequency distribution of T2C periods also changes from system to system.

Keywords: stars: distances; stars: variables: Cepheids; Magellanic Clouds; infrared: stars

Journal Article.  7083 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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