Cepheid-like Supergiants in the Halo

Pulsations in hot supergiants

Massive stars are the cosmic engines that shape and drive our Universe. Many issues such as their formation, their stability and the mass loss effects, are far from being completely understood. Recent ground-based and space observations have shown pulsations in massive MS and post-MS stars, such as acoustic and gravity modes excited by the κ-mechanism and even solar-like oscillations. Theoretic...

The Cepheid Luminosity Scale

Red Supergiants in the Local Group

Galaxies in the Local Group span a factor of 15 in metallicity, ranging from the super-solar M31 to the Wolf-Lundmark-Melotte (WLM) galaxy, which is the lowest-metallicity (0.1Z⊙) Local Group galaxy currently forming stars. Studies of massive star populations across this broad range of environments have revealed important metallicitydependent evolutionary trends, allowing us to test the accurac...

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...

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]...