🚧 Known Issues

[sgossage]

This post serves to highlight current known issues with POSYDON's main branch and is actively updated as we work on solutions.

If you’re affected by any of the issues below or have questions, feel free to open a discussion or an issue and provide further details and/or insight into the issue and how it affects you. If you do so, please provide details such as the version of POSYDON that you are using and as always please feel free to reach out if you need help dealing with an issue.

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1. MESA grid steps can yield H-rich_Core-H_burning stars with He and Carbon/Oxygen cores.

• 🔍Details: In ~0.3% of HMS stars, initial-final interpolation during steps like step_HMS_HMS can mix in post-MS neighbors (e.g., core He burning). This may “pollute” results, producing stars with He or CO cores while still classified as HMS.

• ⚠️Impact: A small percentage of your stars (~0.2% of full population) may have unreliable abundance patterns and progenitor core masses due to this interpolation error. If your results may be sensitive to this, double check the binary histories of such systems to analyze the impact.

• 📊Status: Monitoring (we are tracking the issue and determining the best course of action).

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[astroJeff]

2. Missing H-star - He-star MESA grid.

• 🔍Details: In a minority of cases, some binary systems evolve into a peculiar state where an evolved primary becomes stripped, leaving behind a He-rich star, and then overfills its Roche lobe a second time as a helium giant. We currently lack a grid within POSYDON that can handle the mass transfer from helium stars onto hydrogen stars.

• ⚠️Impact: As these binary systems lack a corresponding MESA grid, they fail with an EvolutionWarning.

• 📊Status: We are working to develop a grid to handle these binaries. In the meantime these binaries will end with a failure.