The anomalous Cepheid XZ Ceti

The anomalous Cepheid XZ Ceti

Aims. XZ Ceti is the only known anomalous Cepheid in the Galactic field. Being the nearest and brightest such variable star, a detailed study of XZ Ceti may shed light on the behaviour of anomalous Cepheids whose representatives have been mostly detected in external galaxies. Methods. CCD photometric and radial velocity observations have been obtained. The actual period and amplitude of pulsati...

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...

The Cepheid Luminosity Scale

On the Cepheid Metallicity Dichotomy

With the aid of stellar atmosphere models, we derive iron abundances [Fe/H] from the OGLE B, V , I photometry on the Magellanic Cloud Cepheids. We show that in both clouds the average metallicities of the first overtone variables are lower than those of the fundamental ones (by ∼ 0.2 and ∼ 0.3 dex in the LMC and SMC, respectively). Consequently, there is a correlation between the overall [Fe/H]...

The photometric period in ES Ceti

We present ULTRACAM photometry of ES Cet, an ultracompact binary with a 620-s orbital period. The mass transfer in systems such as this one is thought to be driven by gravitational radiation, which causes the binary to evolve to longer periods since the semidegenerate donor star expands in size as it loses mass. We supplement these ULTRACAM+William Herschel Telescope (WHT) data with observation...