Head-on collision of unequal mass black holes: close-limit predictions

TL;DR

This paper extends the close-limit approximation to unequal mass black hole collisions, exploring its effectiveness in predicting astrophysical outcomes and understanding its limitations without available numerical relativity data.

Contribution

It applies the close-limit method to unequal mass black hole collisions, analyzing its predictive accuracy and limitations in the absence of numerical relativity results.

Findings

Partial success in estimating energy output and recoil velocities.

Insights into the limitations related to mass measures and validity range.

Highlights the need for further refinement of approximation methods.

Abstract

The close-limit method has given approximations in excellent agreement with those of numerical relativity for collisions of equal mass black holes. We consider here colliding holes with unequal mass, for which numerical relativity results are not available. We try to ask two questions: (i) Can we get approximate answers to astrophysical questions (ideal mass ratio for energy production, maximum recoil velocity, etc.), and (ii) can we better understand the limitations of approximation methods. There is some success in answering the first type of question, but more with the second, especially in connection with the issue of measures of the intrinsic mass of the colliding holes, and of the range of validity of the method.