Surface Chemistry Shows Which Massive Stars Have Gained Mass from Binary Companions

Researchers from the Max Planck Institutes have developed a technique to identify massive stars that have gained mass from binary companions. The method focuses on the surface chemistry of stars, specifically the abundance of elements like helium, carbon, nitrogen, and oxygen. This technique allows them to reconstruct the stellar history of stars that appear solitary, even if they had once been part of a binary system. The key is the CNO abundance diagram, which shows a distinct pattern for mass gainers. The study reveals that stars like Gamma Columbae, which appeared to be stripped-envelope stars, are actually former mass gainers. This method provides a direct window into the hidden lives of stars, allowing astronomers to determine their masses and how efficiently they accreted material from their companions.

• Gamma Columbae is about 1050 light years away, has about six solar masses, and is about 24 million years old.
• It has a high nitrogen-to-carbon ratio, a moderate nitrogen-to-oxygen ratio, and helium enrichment.
• The researchers found that it has about 17% stripped matter.
• The method shows that the star's surface chemistry matches the expected composition for a mass gainer.
• The star's accretion history reveals that it received material from its companion star's core and surface.

The findings have important implications for understanding stellar evolution and galaxy formation. The method helps determine the masses of stars and how much material was accreted, providing insights into the efficiency of mass transfer processes. This information is crucial for understanding how massive stars shape their environments, including the formation of galaxies. The study also highlights the importance of binary systems in mass transfer and how this process affects the life cycles of stars. The results from this study will be used in large-scale surveys to understand the distribution and properties of massive stars in the universe.

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