The evolutionary state of the red giant star L₂ Puppis

Abstract

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.