1997PASP..109..639H

The three dwarf Cepheid variable stars CY Aquarii, XX Cygni, and V798 Cygni were examined with CCD time series ensemble photometry. The Fourier decomposition of the light curves showed no evidence that any of the three stars was a double-mode variable. CY Aqr was fit with a nine term harmonic series with a residual error of 10 mmag. XX Cyg was fit with a ten term harmonic series with a residual error of 10 mmag. V798 Cyg was fit with a four term harmonic series with a residual error of 7 mmag. In addition, we examined a set of double-mode dwarf Cepheids with the same Fourier decomposition techniques. We present evidence that these double-mode dwarf Cepheids fill the gap in the amplitude ratio distribution reported by Antonello et al.(1986) and Poretti et al.(1990).