Stellar spin may dictate the decay of black hole flares
New research suggests the initial rotation of a star influences how quickly radiation fades during tidal disruption events.
The fading of radiation from black hole flares may be directly linked to the initial spin of the stars being consumed. This discovery provides a new window into the chaotic environments surrounding supermassive black holes and the specific properties of the stars they destroy.
Researchers from Syracuse University have found that the decay of repeated flares in repeating partial tidal disruption events (rpTDEs) is tied to the star's original rotation. According to the study, stars that are already spinning rapidly before their first encounter with a black hole do not experience the same "spin-up" effect as non-spinning stars. Because these rapidly spinning stars avoid this additional acceleration, the resulting flares grow progressively dimmer as the star continues to lose mass over time.
The mechanics of disruption
These flares typically occur during Tidal Disruption Events, where a star wanders too close to a supermassive black hole and is ripped apart by immense tidal forces. The resulting debris forms an accretion disk, which emits intense radiation before eventually fading. In the case of partial disruptions, the star survives the initial encounter but returns periodically to be stripped of more material, creating a series of flares.
Why stellar rotation matters
Understanding the role of stellar spin allows astrophysicists to better model the environment around supermassive black holes and refine their understanding of how matter is consumed in the universe. By observing the specific rate at which a flare's intensity decays, researchers may be able to work backward to determine the original properties of the disrupted star, such as its initial angular momentum.
Implications for galactic evolution
This research also provides critical insight into the origin of stars found in tight orbits around supermassive black holes. The dynamics observed in these events may be linked to the Hills mechanism, a process where a binary star system is disrupted, leaving one star captured in a close orbit while the other is ejected from the galaxy. This connection helps scientists map the lifecycle of stars in the most extreme gravitational environments in the cosmos.