English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Knowledge of the spin of the black hole resulting from the merger of ageneric black-hole binary is of great importance for studying the cosmologicalevolution of supermassive black holes. Several attempts have been made to modelthe spin via simple expressions exploiting the results of numerical-relativitysimulations. While these expressions are in reasonable agreement with thesimulations, they neglect the precession of the binary's orbital plane, andcannot therefore be applied directly -- i.e., without evolving the system tosmall separations using post-Newtonian theory -- to binaries with separationslarger than a few hundred gravitational radii. While not a problem inprinciple, this may be impractical if the formulas are employed in cosmologicalmerger-trees or N-body simulations, which provide the spins and angularmomentum of the two black holes when their separation is of hundreds orthousands of gravitational radii. The formula that we propose is instead builton improved assumptions and gives, for any separation, a very accurateprediction both for the norm of the final spin and for its direction. Bycomparing with the numerical data, we also show that the final-spin directionis very accurately aligned with the binary's total angular momentum at largeseparation. Hence, observations of the final-spin direction (e.g. via a jet)can provide information on the binary's orbital plane at large separations andcould be relevant, for instance, for studying X-shaped radio sources.

Predicting the direction of the final spin from the coalescence of two black holes