Tests of Gravitational-Wave Birefringence with the Gravitational-Wave Catalog

Yi-Fan Wang^{1, 2}, Stephanie M. Brown^{1, 2}, Lijing Shao^{3, 4}, Wen Zhao^{5, 6}

_{1. Max-Planck-Institut for Gravitationsphysik (Albert-Einstein-Institut), D-30167 Hannover, Germany 2. Leibniz Universitat Hannover, D-30167 Hannover, Germany 3. Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China 4. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China 5. CAS Key Laboratory for Researches in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026, China 6. School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China}

Introduction

We report the results of testing gravitational-wave birefringence using the largest population of gravitational-wave events currently available. Gravitational-wave birefringence, which can arise from the effective field theory extension of general relativity, occurs when the parity symmetry is broken, causing the left- and right-handed polarizations to propagate following different equations of motion. We perform Bayesian inference on the ninety-four events reported by the 4th-Open Gravitational-wave Catalog (4-OGC) using a parity-violating waveform. We find no evidence for a violation of general relativity in the vast majority of events. However, the most massive event, GW190521, and the second most massive event, GW191109, show intriguing non-zero results for gravitational-wave birefringence. We find that the probability of association between GW190521 and the possible electromagnetic (EM) counterpart reported by Zwicky Transient Facility (ZTF) is increased when assuming birefringence. Excluding GW190521 and GW191109, the parity-violating energy scale is constrained to $M_\mathrm{PV} > 0.05$ GeV at $90%$ credible interval, which is an improvement over previous results from twelve events by a factor of five. We discuss the implications of our results on modified gravity and possible alternative explanations such as waveform systematics. More detections of massive binary black hole mergers from the upcoming LIGO/Virgo/KAGRA run will shed light on the true origin of the apparent birefringence.

Waveform template

To install the PyCBC waveform template for testing gravitational-wave birefringence, refer to https://github.com/yi-fan-wang/TestingGR_with_Gravwaves. The waveform is described in the paper: Waveform of gravitational waves in the general parity-violating gravities (Zhao et al.)

License and Citation

This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 United States License.

This is work is published in Phys. Rev. D 106, 084005 (with open access funded by the Max Planck Society). We encourage use of these data in derivative works. If you use the material provided here, please cite the paper using the reference:

@article{Wang:2021gqm,
    author = "Wang, Yi-Fan and Brown, Stephanie M. and Shao, Lijing and Zhao, Wen",
    title = "{Tests of gravitational-wave birefringence with the open gravitational-wave catalog}",
    eprint = "2109.09718",
    archivePrefix = "arXiv",
    primaryClass = "astro-ph.HE",
    doi = "10.1103/PhysRevD.106.084005",
    journal = "Phys. Rev. D",
    volume = "106",
    number = "8",
    pages = "084005",
    year = "2022"
}