Hierarchical constraints on gravitational waves from horizonless compact objects
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 meters above the horizon.
Cite
@article{arxiv.2506.17215,
title = {Hierarchical constraints on gravitational waves from horizonless compact objects},
author = {Rajrupa Mondal and Julian Westerweck and Yotam Sherf and Collin D. Capano and Ram Brustein},
journal= {arXiv preprint arXiv:2506.17215},
year = {2026}
}