The evolutionary state of the red giant star L2 Puppis

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Context. L2 Puppis (L2 Pup) is a nearby red giant star and an important object in late-type star research because it has a dust disc and potentially a companion. Aims. L2 Pup is often called the second-closest asymptotic giant branch (AGB) star to the sun, second only to R Doradus. However, whether the star is indeed on the AGB or the red giant branch (RGB) is questionable. We review its evolutionary state. Methods. We analysed high-resolution optical archive spectra to search for absorption lines of the third dredge-up indicator technetium (Tc) in L2 Pup. We also compared the star to a sample of well-known AGB stars in terms of luminosity and pulsation properties and placed it in a Gaia-2MASS diagram. Results. L2 Pup is found to be Tc-poor. Thus, it is not undergoing third dredge-up events. The star is fainter than the RGB tip and fainter than all Tc-rich stars in the comparison sample. L2 Pup pulsates in the fundamental mode, similar to Mira variables, but its pulsation properties do not allow us to distinguish between the RGB and AGB stages. Conclusions. In conclusion, L2 Pup could be an RGB or early AGB star, but it is more likely to be an RGB than an AGB star. Our findings are important for a better understanding of the L2 Pup system and its past and future evolution.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.