Binary-black hole spin population results may be driven by prior degeneracies
Abstract
Gravitational waves carry information on the spins of merging binary-black holes. The orientations of their spins relative to their orbits ("tilts")---while challenging to measure---differentiate the astrophysical formation mechanisms by which merging black hole binaries may form. Multiple analyses have reported tentative evidence that black hole spins are preferentially oriented in the plane of the binary orbit. We show that these results are likely extrapolated from more easily measurable "effective spin" parameters which characterize the gravitational-wave inspiral of black hole binaries but may not uniquely constrain their astrophysical formation. In particular, we reproduce a peak in the spin tilt distribution with information about the marginal effective spin distributions alone. We propose a geometric picture to compare constraints on effective spins to standard population modeling assumptions, suggesting that current inferences of a preferred spin orientation are spurious.
Related
- Evolution of Massive Main-Sequence Stars in Binary Population Synthesis. II. Consequences for Black Hole High-Mass X-ray Binaries and Binary Black Holes
- The Loud Tail of the Supermassive Black Hole Binary Population: Multimessenger Candidates and Prospects for SKAO
- Ultralight Bosons Explain the Mass-Spin Correlations in the Merging Binary Black Hole Population
- Bridging the Population Synthesis of Supermassive Binary Black Holes and the Gravitational Wave Background
- Population of Binary Black Holes Inferred from One Hundred and Fifty Gravitational Wave Signals
BibTeX
@misc{wolfe2026binaryblack,
title = {{Binary-black hole spin population results may be driven by prior degeneracies}},
author = {Noah E. Wolfe and Asad Hussain and Jack Heinzel and Salvatore Vitale},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10753},
eprint = {2609.10753},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10753},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Binary-black hole spin population results may be driven by prior degeneracies
AU - Noah E. Wolfe
AU - Asad Hussain
AU - Jack Heinzel
AU - Salvatore Vitale
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2609.10753
UR - https://arxiv.org/abs/2609.10753
AB - Gravitational waves carry information on the spins of merging binary-black holes. The orientations of their spins relative to their orbits ("tilts")---while challenging to measure---differentiate the astrophysical formation mechanisms by which merging black hole binaries may form. Multiple analyses have reported tentative evidence that black hole spins are preferentially oriented in the plane of the binary orbit. We show that these results are likely extrapolated from more easily measurable "effective spin" parameters which characterize the gravitational-wave inspiral of black hole binaries but may not uniquely constrain their astrophysical formation. In particular, we reproduce a peak in the spin tilt distribution with information about the marginal effective spin distributions alone. We propose a geometric picture to compare constraints on effective spins to standard population modeling assumptions, suggesting that current inferences of a preferred spin orientation are spurious.
ER -