What Can Happen When a Rapidly Spinning Star Meets a Black Hole?

Astrophysicists at Syracuse University have discovered that the dimming of flares in repeating partial tidal disruption events (rpTDEs) may be linked to the spin of the star itself. The team found that stars with higher spin rates produce dimmer flares, which could explain why some rpTDEs remain dim despite repeated close encounters with black holes. The findings suggest that the spin of a star influences the amount of material it loses to the black hole, affecting the brightness of the resulting flares. The researchers used hydrodynamical simulations to explore how a star's spin could affect the tidal stripping process, and they found that a star with a high spin rate does not get spun up more during each encounter, keeping the amount of material lost consistent. This could explain why some rpTDEs remain dim. The team also considered the Hills mechanism, which describes binary star systems where one star is captured by a black hole and retains its high spin rate. If such stars exist around Sagittarius A*, their behavior could provide insights into how their spin influences the dimming of flares as they orbit closer to the black hole.

• Ananya Bandopadhyay, doctoral student, and Benjamin Amend, postdoctoral researcher, worked with Eric Coughlin, associate professor, to analyze the dimming flares.
• The team observed that four out of ten rpTDEs showed dim flares that did not match predictions based on mass loss.
• The researchers considered the star's spin rate and the Hills mechanism, which involves binary star systems where one star is captured by a black hole.
• The simulations showed that a star with a high spin rate does not get spun up more during each encounter, maintaining consistent material loss.
• The findings suggest that a star's spin plays a role in the brightness of the flares, and that such stars might be the ones with high spin rates observed in rpTDEs.
• The team also noted that the Hills mechanism could explain how a star's spin is retained even after being captured by a black hole.
• The study highlights the importance of stellar spin in understanding the behavior of rpTDEs and how it influences the dimming of flares.

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