Internal synchronization of the Feige 64 BHB star

Determine whether the interior of the blue horizontal branch component of the Feige 64 binary system has achieved synchronous rotation with the 0.8262782-day orbital period.

Background

The authors infer that the surface of Feige 64’s blue horizontal branch component is likely synchronized with the binary orbit because the projected rotational velocity predicted under synchronous rotation agrees with the spectroscopic measurement. However, the available light curve constrains the surface-related rotational state but does not provide sufficient information about the star’s internal rotation period. Consequently, whether synchronization extends from the surface into the interior remains unresolved.

References

However, the current light curve does not provide sufficient information to constrain the internal rotation period, and therefore, it remains unclear whether the interior has also achieved synchronous rotation.

— A Helium-shell Burning Blue Horizontal Branch Star Produced from Common Envelope Evolution  (2608.11557 - Li et al., 12 Aug 2026) in Section 3, subsection “Light curve fitting” (label: sec:lcfit)