Evolutionary stages of blue supergiant star HD 74371 revealed by light patterns

Blue supergiants represent a critical phase in the life of massive stars, yet their exact history remains difficult to pin down. By analyzing brightness fluctuations in HD 74371 and five other stars, researchers have utilized asteroseismology to determine their evolutionary status. The findings suggest that HD 74371 is currently moving through a specific post-red supergiant phase of its development.

Star system: HD 74371 | Distance from the Sun: 5445 light years

Blue supergiants are massive, luminous stars that play a vital role in our understanding of how stars evolve and age. Distinguishing whether a blue supergiant is in an early stage of its life or has already passed through a red supergiant phase is a complex challenge. By studying the rhythmic pulsations or brightness changes of these stars, experts can gain insights into their internal structure, mass, and overall evolutionary status. This process, known as asteroseismology, uses the way a star vibrates to reveal what is happening deep within its core.

To better understand these massive objects, light curves from the TESS space telescope were analyzed to detect periodic brightness variations. These measurements were combined with theoretical models of unstable radial vibrations, known as strange modes, to estimate the mass of each star. Researchers also applied advanced mathematical tools, such as the Lomb-Scargle periodogram and weighted wavelet Z-transforms, to interpret the complex, time-varying signals in the light data. This approach allows for a clearer view of the star's current physical state compared to its predicted life cycle.

The findings indicate that HD 74371 and HD 79186 are moving in a blue-ward direction after having passed through a red supergiant phase. Other stars in the sample, such as HD 52382 and HD 99953, also appear to be in a post-red supergiant state, though their measured masses do not align perfectly with current theoretical models. Meanwhile, HD 80077 shows a significant mass discrepancy, suggesting its development is more complex than standard models currently account for. These results emphasize that while asteroseismology is a powerful diagnostic tool, further study is needed to resolve the differences between observation and theory.

Key findings
HD 74371 and HD 79186 are currently evolving in a blue-ward direction following their red supergiant phase.
HD 52382 and HD 99953 are likely in a post-red supergiant phase, although their measured masses challenge existing evolutionary models.
The extreme supergiant HD 80077 exhibits the largest mass discrepancy, indicating a highly complex evolutionary history.
Asteroseismology serves as a valuable, though still developing, tool for constraining the status of massive blue supergiant stars.
Stochastic low-frequency variability, or random brightness fluctuations, did not provide a reliable way to determine the evolutionary stage of these stars.

Scientific study

Photometric variability of blue supergiants: Constraints on stellar masses and evolutionary stages (external link)