Unveiling the Chemical Secrets of Anomalous Cepheids: Insights from High-Resolution Spectroscopy

Anomalous Cepheids (ACEPs) are short-period variable stars with periods ranging from a few hours to two days. They are relatively massive (1-2 Msun, metal-deficient, and frequently found in dwarf galaxies. Their origin is attributed to either low-metallicity environments or binary mergers. In our initial spectroscopic investigation of these objects, we examined the origin of a sample of 12 Galactic ACEPs, determining their chemical abundance through high-resolution spectroscopy. We discovered a surprising enhancement in sodium abundance, a feature also observed in Galactic Globular Clusters. This finding was interpreted within a scenario where the investigated ACEPs formed in binary systems involving mass exchange via Roche Lobe overflow. Motivated by these results, we initiated a survey of all ACEPs bright enough to be observed with high-resolution spectrographs at 4-8m telescopes. In this contribution, I present the preliminary results of this project, based on a sample of more than 40 Galactic ACEPs.