Monday, December 4, 2023

Study Reveals Birth Characteristics of Collapsar Black Holes


(Direct collapse black holes (DCBHs) are massive black hole seeds theorized to have formed in the high-redshift Universe and with typical masses at formation of ~105 M ☉, but spanning between 104 M and 106 M ☉)

The universe is full of mysteries, and black holes are among the most intriguing objects in space. These cosmic phenomena have always fascinated astronomers and astrophysicists due to their fascinating properties, such as their immense gravitational pull and the fact that nothing, not even light, can escape their grasp.

Recently, researchers have been studying a specific type of black hole, known as a collapsar black hole. These black holes are formed from the collapse of massive stars, which creates a proto-neutron star. As the star collapses under its own gravity, it releases a tremendous amount of energy that is channeled into the launch of relativistic jets that power the black hole’s spin.

In a recent study, Ore Gottlieb and his team of researchers from various institutions across the globe have shown that theoretical considerations, combined with gamma-ray burst (GRB) observations, support the idea that collapsar black holes are born slowly spinning.

The team’s findings indicate that once a black hole becomes saturated with large-scale magnetic flux, the power of its jets is solely dictated by the black hole’s spin and mass accretion rate. Recent core-collapse simulations support this theory, and GRB observations have suggested that black holes associated with jets are typically born with low spins.

The researchers found that rapidly spinning black holes produce jets with excessive power, indicating that the majority of black holes associated with jets are born with a dimensionless spin of about 0.2, or 0.5 for wobbling jets. This finding could be applied to the entire core-collapse black hole population, unless there is an anti-correlation between the stellar magnetic field and angular momentum.

In a companion paper, the team showed that regardless of the black hole’s natal spin, the extraction of rotational energy ultimately leads to an inevitable spin-down to below 0.2. These results are consistent with recent gravitational wave observations of black hole mergers that indicate low spins.

The team’s research was supported by 3D general relativistic magnetohydrodynamic simulations of collapsar jets with characteristic GRB energies, powered by slowly spinning black holes. The team found that jets of typical GRB power do not retain their energy during propagation in the star, providing the first numerical indication that many jets might fail to generate a GRB.

The team’s research has significant implications for our understanding of the universe and the formation of black holes. By understanding how these black holes are born and evolve, we can learn more about the nature of the universe and the processes that govern it.

In conclusion, the research conducted by Ore Gottlieb and his team sheds new light on the nature of collapsar black holes and how they form. Their findings have important implications for our understanding of the universe and the processes that govern it. As we continue to explore the mysteries of the cosmos, we can look forward to new discoveries and a deeper understanding of the world around us.



Source: Gottlieb, O., Jacquemin-Ide, J., Lowell, B., Tchekhovskoy, A., & 
Ramirez-Ruiz, E. (2023). Collapsar Black Holes are Born Slowly Spinning.

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