The Unusual Pulsating Variable XZ Ceti

The peculiar pulsating variable XZ Ceti has a period of 0.8231 day, suggesting that it is a Bailey type ab RR Lyrae star, but it has a light curve shape and amplitude which is like that of the Bailey type c variables. Fourier decomposition analysis verifies that the parameters of its light curve match those of the type c variables, except for its unacceptably long period. We have obtained a new photometric light curve which verifies this long period. We have also obtained energy distributions from spectrum scans, which are used to derive a temperature and approximate surface gravity of this star. These results are used to construct pulsation models so as to attempt to identify the. nature of XZ Ceti. The models suggest the possibility that XZ Ceti is an anomalous Cepheid or, perhaps, an overtone BL Her star. Subject headings: stars: individualstars: pulsation stars: RR Lyrae