Lambda Bootis phenomenon identified in the massive early B-type star HD 37356

Star system: HD 37356 | Distance from the Sun: 1484 light years

The Lambda Bootis phenomenon is a unique chemical condition in stars where certain elements, known as refractory elements (materials that condense at high temperatures, such as iron), are significantly less abundant than expected, while volatile elements remain at normal levels. This feature has now been identified in the massive early B-type star HD 37356, marking the first time this characteristic has been observed in such a massive stellar object.

Researchers analyzed high-quality spectra of the star using complex mathematical models that simulate how starlight interacts with its atmosphere. By comparing these results with synthetic spectra generated through advanced neural networks, they were able to determine the specific elemental abundances within the star's outer layers.

To derive the fundamental properties of the star, the team utilized data from the Gaia space observatory alongside stellar evolution models. The analysis showed that HD 37356 is remarkably similar to the standard star Gamma Pegasi, with the notable exception of its weaker refractory element lines. This lower iron content directly influences the star's pulsational behavior, causing it to differ from its stellar twin.

The findings suggest that the most plausible explanation for this phenomenon is the accretion of gas depleted of refractory elements from a circumstellar disk during the star's formation. This process is only possible if HD 37356 rotates very slowly, preventing internal mixing currents from washing away these distinct chemical signatures.

Key findings
- First detection of the Lambda Bootis phenomenon in a massive early B-type star.
- Refractory elements in HD 37356 are depleted by 0.25 to 0.45 dex compared to cosmic standards.
- Volatile element abundances in the star are consistent with standard cosmic levels.
- Lower iron levels in the star account for its distinct pulsational patterns.
- Formation likely involved the accretion of gas from a disk during star formation, requiring a slow rotation rate.

Scientific study

Discovery of the λ Bootis phenomenon in an early B-type star (external link)