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

TL;DR

This study investigates the evolutionary stage of the nearby red giant star L$_2$ Puppis, using spectral analysis and comparison with known stellar samples, concluding it is more likely an RGB star than an AGB star.

Contribution

The paper provides the first detailed spectral analysis of L$_2$ Puppis to determine its evolutionary stage, clarifying its position in stellar evolution.

Findings

L$_2$ Pup is Tc-poor, indicating no third dredge-up events.

L$_2$ Pup is fainter than the RGB tip and Tc-rich stars.

The star pulsates in the fundamental mode, similar to Mira variables.

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