Black Hole Spectroscopy and Tests of General Relativity with GW250114

Area of Science:

• * Astrophysics
• * Gravitational-wave astronomy
• * General relativity

Background:

• * Binary black hole mergers produce gravitational waves, offering insights into extreme gravity.
• * The loudest detected signal, GW250114, presents a unique opportunity to test general relativity (GR).
• * Black hole remnants emit characteristic quasinormal modes (QNMs) upon perturbation.

Purpose of the Study:

• * To test Einstein's general relativity (GR) in the high-velocity, strong-gravity regime using the GW250114 signal.
• * To determine if the merger remnant conforms to the Kerr metric, predicted by GR.
• * To utilize black hole spectroscopy for stringent verification of GR.

Main Methods:

• * Analyzed the postmerger gravitational wave signal GW250114.
• * Identified and analyzed quasinormal modes (QNMs) in the signal.
• * Constrained the spectroscopic pattern of dominant quadrupolar (ℓ=m=2) mode and its overtone against Kerr predictions.
• * Fitted a parametrized waveform encompassing the inspiral-merger-ringdown sequence.

Main Results:

• * At least two quasinormal modes were required to explain the GW250114 data.
• * Mode amplitudes and phases align with numerical relativity simulations.
• * Constrained the fundamental (ℓ=m=4) mode to tens of percent and quadrupolar frequency to within a few percent of GR predictions.
• * Achieved single-event constraints 2-3 times more stringent than previous catalog combination.

Conclusions:

• * GW250114 provides the most stringent single-event verification of GR and the Kerr nature of black holes to date.
• * Black hole spectroscopy is a powerful tool for future gravitational-wave observations.
• * The study confirms the predictive power of GR in extreme astrophysical environments.