V363 Cas: a new lithium rich Galactic Cepheid

TL;DR

This study identifies V363 Cas as a lithium-rich Galactic Cepheid, providing detailed stellar parameters and suggesting it is in its first crossing of the instability strip, which offers insights into stellar evolution and lithium enrichment.

Contribution

The paper reports the discovery of lithium enrichment in V363 Cas and analyzes its evolutionary status, highlighting its first crossing of the instability strip among Galactic Cepheids.

Findings

V363 Cas is lithium-rich with A(Li)=2.86 dex.

The period of V363 Cas is increasing, indicating first crossing of the instability strip.

V363 Cas likely evolved from a slowly-rotating progenitor.

Abstract

Classical Cepheids (DCEPs) are important astrophysical objects not only as standard candles in the determination of the cosmic distance ladder, but also as a testbed for the stellar evolution theory, thanks to the strict connection between their pulsation [period(s), amplitudes] and stellar (luminosity, mass, effective temperature, metallicity) parameters. We aim at unveiling the nature of the Galactic DCEP V363 Cas and other DCEPs showing cosmic abundances of lithium in their atmospheres. We have collected three epochs high-resolution spectroscopy for V363 Cas with HARPS-N@TNG. Accurate stellar parameters: effective temperatures, gravities, micro-turbulences, radial velocities, and metal abundances were measured for this star. We detected a lithium abundance of A(Li)=2.86+-0.10 dex, along with iron, carbon and oxygen abundances of [Fe/H]=-0.30+-0.12 dex, [C/H]=-0.06+-0.15 dex and [O/H]=0.00+-0.12 dex. V363 Cas is the fifth among the Milky Way DCEPs to exhibit a Li-rich feature. An analysis of historical time-series spanning a hundred year interval shows that the period of V363 Cas is increasing, with a sharp acceleration after HJD=2453000. This is a clear hint of first crossing of the instability strip. Our results favour the scenario in which the five Galactic Li-rich DCEPs are first-crossing the instability strip having had slowly-rotating progenitors during their main sequence phase.