Yellow and Red Supergiants in the Large Magellanic Cloud

TL;DR

This study identifies and analyzes yellow and red supergiants in the Large Magellanic Cloud, demonstrating that updated Geneva models accurately predict their locations and lifetimes, improving understanding of stellar evolution.

Contribution

It extends previous research by analyzing LMC supergiants using proper motions and radial velocities, confirming the accuracy of new Geneva evolutionary models for these stars.

Findings

Successfully identified 317 probable yellow supergiants

Foreground contamination was reduced to 3% for red supergiants

Geneva models accurately predict supergiant locations and lifetimes

Abstract

Due to their transitionary nature, yellow supergiants provide a critical challenge for evolutionary modeling. Previous studies within M31 and the SMC show that the Geneva evolutionary models do a poor job at predicting the lifetimes of these short-lived stars. Here we extend this study to the LMC while also investigating the galaxy's red supergiant content. This task is complicated by contamination by Galactic foreground stars that color and magnitude criteria alone cannot weed out. Therefore, we use proper motions and the LMC's large systemic radial velocity (\sim278 km/s) to separate out these foreground dwarfs. After observing nearly 2,000 stars, we identified 317 probable yellow supergiants, 6 possible yellow supergiants and 505 probable red supergiants. Foreground contamination of our yellow supergiant sample was \sim80%, while that of the the red supergiant sample was only 3%. By placing the yellow supergiants on the H-R diagram and comparing them against the evolutionary tracks, we find that new Geneva evolutionary models do an exemplary job at predicting both the locations and the lifetimes of these transitory objects.