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arXiv · 2506.17215

Hierarchical constraints on gravitational waves from horizonless compact objects

Rajrupa Mondal·Julian Westerweck·Yotam Sherf·Collin D. Capano·Ram Brustein
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Abstract

We use the data of several promising gravitational wave observations to obtain increasingly stringent bounds on near-horizon deviations of their sources from the Kerr geometry. A range of horizonless compact objects proposed as alternatives to black holes of general relativity would possess a modified gravitational wave emission after the merger. Modelling these objects by introducing reflection of gravitational waves near the horizon, we can measure deviations from Kerr in terms of a single additional parameter, the location of the reflection. We quote bounds on deviations for 5 events in addition to previous results obtained for GW150914. Additionally, we improve upon previous results by hierarchically combining information from all analysed events, yielding a bound on deviations of less than $2.5 \times 10^{-26}$ meters above the horizon.

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Rajrupa Mondal, Julian Westerweck, Yotam Sherf, Collin D. Capano, Ram Brustein. 2025-06-20. Hierarchical constraints on gravitational waves from horizonless compact objects. https://arxiv.org/abs/2506.17215

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