Period-luminosity relations of type II Cepheids in the Magellanic Clouds
  Period-luminosity relations (PLRs) of type II Cepheids (T2Cs) in the Small
Magellanic Cloud are derived based on OGLE-III, IRSF/SIRIUS and other data, and
these are compared with results for the Large Magellanic Cloud 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.
