TY - JOUR
T1 - Aberration of gravitational waveforms by peculiar velocity
AU - Bonvin, Camille
AU - Cusin, Giulia
AU - Pitrou, Cyril
AU - Mastrogiovanni, Simone
AU - Congedo, Giuseppe
AU - Gair, Jonathan
N1 - Funding Information:
We thank Nicola Tamanini for interesting discussions and exchanges, Ruth Durrer for valuable discussions and feedback during the early stage of this project, Clifford Will for comments on transformation properties in more general metric theories and Guillaume Faye for discussions on post-Newtonian expansions of waveforms. CB acknowledges support from the Swiss National Science Foundation and from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 863929; project title ‘Testing the law of gravity with novel large-scale structure observables’. The work of GC is funded by Swiss National Science Foundation (Ambizione grant Gravitational wave propagation in the clustered Universe) and by CNRS. For the purpose of open access, the authors have applied a Creative Commons Attribution (CC BY) licence to any author accepted manuscript version arising from this submission.
Publisher Copyright:
© 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2023/10/1
Y1 - 2023/10/1
N2 - One key prediction of General Relativity is that gravitational waves are emitted with two independent polarizations. Any observation of extra polarization mode, spin-1 or spin-0, is consequently considered a smoking gun for deviations from General Relativity. In this paper, we show that the velocity of merging binaries with respect to the observer gives rise to spin-1 polarization in the observer frame even in the context of General Relativity. These are pure projection effects, proportional to the plus and cross polarizations in the source frame, hence they do not correspond to new degrees of freedom. We demonstrate that the spin-1 modes can always be rewritten as pure spin-2 modes coming from an aberrated direction. Since gravitational waves are not isotropically emitted around binary systems, this aberration modifies the apparent orientation of the binary system with respect to the observer: the system appears slightly rotated due to the source velocity. Fortunately, this bias does not propagate to other parameters of the system (and therefore does not spoil tests of General Relativity), since the impact of the velocity can be fully reabsorbed into new orientation angles.
AB - One key prediction of General Relativity is that gravitational waves are emitted with two independent polarizations. Any observation of extra polarization mode, spin-1 or spin-0, is consequently considered a smoking gun for deviations from General Relativity. In this paper, we show that the velocity of merging binaries with respect to the observer gives rise to spin-1 polarization in the observer frame even in the context of General Relativity. These are pure projection effects, proportional to the plus and cross polarizations in the source frame, hence they do not correspond to new degrees of freedom. We demonstrate that the spin-1 modes can always be rewritten as pure spin-2 modes coming from an aberrated direction. Since gravitational waves are not isotropically emitted around binary systems, this aberration modifies the apparent orientation of the binary system with respect to the observer: the system appears slightly rotated due to the source velocity. Fortunately, this bias does not propagate to other parameters of the system (and therefore does not spoil tests of General Relativity), since the impact of the velocity can be fully reabsorbed into new orientation angles.
KW - cosmology: theory
KW - gravitational waves
UR - https://www.scopus.com/pages/publications/85168655688
U2 - 10.1093/mnras/stad1907
DO - 10.1093/mnras/stad1907
M3 - Article
AN - SCOPUS:85168655688
SN - 0035-8711
VL - 525
SP - 476
EP - 488
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -