Photometry of type II Cepheids. II. The short-period stars

We present 668 new photometric observations for 24 Cepheids with periods less than 3 days. Most of the stars are probable type II Cepheids, but we have included some type I Cepheids for comparison. A discussion of the Fourier parameters of the light curves leads to the conclusion that they can be used to distinguish among the several types of light curves found among the type II stars but are of limited usefulness for distinguishing between type I and type II Cepheids. The pulsational stability is investigated by searching for long-term changes in the light-curve shapes, period changes, and light-curve scatter. In terms of these parameters, the pulsation is more stable than those that were found for the long-period stars, but for each there are several stars that show unusually large effects. However, there does not seem to be any obvious difference in light-curve stability of type II Cepheids compared with type I Cepheids.