Biases from Astrophysical Environmental Effects in Standard-Siren Cosmology
Abstract
Next-generation ground based gravitational wave detectors will enable precision standard-siren cosmology, making systematics increasingly important. We investigate how line-of-sight acceleration, as may arise for compact binaries in dense astrophysical environments, biases measurements of the Hubble constant H0. We simulate a catalogue of 50 binary neutron star bright sirens with known host redshifts, assuming the signals have been impacted by line-of-sight acceleration and analysing them with vacuum waveforms. Unmodelled line-of-sight acceleration biases the inferred luminosity distances and shifts the individual H0 posteriors systematically towards lower values. Consequently, combining events narrows the posterior around a biased value rather than averaging away the systematic, even when the acceleration signs are assigned randomly. For our 50-event catalogues, affected fractions of approximately 10% at |a∥|/c=10−6 s−1, or 30% at |a∥|/c=10−7 s−1, produce offsets exceeding three posterior standard deviations in at least one quarter of the realisations. Considering larger catalogues further increases the significance of the effect. Our results indicate that environmental effects may constitute an important systematic for precision standard-siren cosmology and should be incorporated into future population analyses.
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BibTeX
@misc{liodis2026biases,
title = {{Biases from Astrophysical Environmental Effects in Standard-Siren Cosmology}},
author = {Ioannis Liodis and Rodrigo Vicente and Soumen Roy and Samaya Nissanke},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.24476},
eprint = {2609.24476},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.24476},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Biases from Astrophysical Environmental Effects in Standard-Siren Cosmology
AU - Ioannis Liodis
AU - Rodrigo Vicente
AU - Soumen Roy
AU - Samaya Nissanke
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.24476
UR - https://arxiv.org/abs/2609.24476
AB - Next-generation ground based gravitational wave detectors will enable precision standard-siren cosmology, making systematics increasingly important. We investigate how line-of-sight acceleration, as may arise for compact binaries in dense astrophysical environments, biases measurements of the Hubble constant H_0. We simulate a catalogue of 50 binary neutron star bright sirens with known host redshifts, assuming the signals have been impacted by line-of-sight acceleration and analysing them with vacuum waveforms. Unmodelled line-of-sight acceleration biases the inferred luminosity distances and shifts the individual H_0 posteriors systematically towards lower values. Consequently, combining events narrows the posterior around a biased value rather than averaging away the systematic, even when the acceleration signs are assigned randomly. For our 50-event catalogues, affected fractions of approximately 10% at |a_∥|/c=10^−6 s^−1, or 30% at |a_∥|/c=10^−7 s^−1, produce offsets exceeding three posterior standard deviations in at least one quarter of the realisations. Considering larger catalogues further increases the significance of the effect. Our results indicate that environmental effects may constitute an important systematic for precision standard-siren cosmology and should be incorporated into future population analyses.
ER -