The evolutionary state of the red giant star L${}_2$ Puppis

Abstract

Context: L${}_2$ Puppis (L${}_2$ 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: L${}_2$ 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 analyse high-resolution optical archive spectra to search for absorption lines of the third dredge-up indicator technetium (Tc) in L${}_2$~Pup. We also compare the star to a sample of well-known AGB stars in terms of luminosity and pulsation properties and place it in a Gaia-2MASS diagram. Results: L${}_2$ 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. L${}_2$ 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, L${}_2$ 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 L${}_2$ Pup system and its past and future evolution

8 pages, 4 figures, accepted for publication in Astronomy & Astrophysics

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