Orateur
Description
The LISA constellation offers a unique opportunity to detect EMRIs, with a sensitivity band that is particularly well suited to these sources. Their detection will not only allow us to probe the intrinsic properties and immediate environments of black holes in the local Universe, but also to use these sources as “dark sirens” for cosmological studies \cite{colpi2024lisa}.
To fully exploit EMRI observations, rapid and reliable sky localization is crucial. It enables the triggering of alerts for electromagnetic observatories, which complements the observation of these complex systems through a multi-messenger approach \cite{kocsis2011observable}. In this context, we present a fast and agnostic localization method.
This approach relies on the construction of a TDI observable, the coronagraphic variable $\kappa$, derived from linear combinations of Sagnac-type channels \cite{costa2025sky}. The principle is as follows: when the direction and frequency parameters injected into the observable exactly match the true source parameters, the gravitational-wave signal is canceled within the $\kappa$ variable. Localization is thus performed by scanning the celestial sphere to identify the configuration that minimizes the spectral power of the signal.
This method also allows for constraining the source localization parameters in an agnostic way, without directly relying on precise waveform models.
The implementation of this approach within the Nullstream pipeline has already demonstrated promising results for MBHBs \cite{costa2025coronagraphic}. This study validates the extension of the method to EMRI signals. In the presence of noise, we show that the method remains robust, notably because EMRIs exhibit a slow frequency evolution, allowing them to remain for long durations within the optimal sensitivity band.
Finally, this work opens perspectives on handling non-stationary noise and raises an important question for LISA data analysis: to what extent can the persistent and complex signal of EMRIs influence or bias the detection and characterization of other transient sources, such as MBHBs?
REFERENCES :
@inproceedings{costa2025sky,
title={Sky Localization of Massive Black Hole Binaries with LISA: Applying Coronagraphic Time-delay Interferometry to Low-latency Searches},
author={Costa Barroso, R and Lemi{`e}re, Y and Mauger, F and Baghi, Q},
booktitle={SF2A-2025: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics. Eds.: A. Siebert},
pages={413--416},
year={2025}
}
@article{colpi2024lisa,
title={LISA definition study report},
author={Colpi, Monica and Danzmann, Karsten and Hewitson, Martin and Holley-Bockelmann, Kelly and Jetzer, Philippe and Nelemans, Gijs and Petiteau, Antoine and Shoemaker, David and Sopuerta, Carlos and Stebbins, Robin and others},
journal={arXiv preprint arXiv:2402.07571},
year={2024}
}
@article{kocsis2011observable,
title={Observable signatures of extreme mass-ratio inspiral black hole binaries embedded in thin accretion disks},
author={Kocsis, Bence and Yunes, Nicol{\'a}s and Loeb, Abraham},
journal={Physical Review D—Particles, Fields, Gravitation, and Cosmology},
volume={84},
number={2},
pages={024032},
year={2011},
publisher={APS}
}
@article{costa2025coronagraphic,
title={Coronagraphic time-delay interferometry: characterization and updated geometric properties},
author={Costa Barroso, Raissa and Lemi{`e}re, Yves and Mauger, Fran{\c{c}}ois and Baghi, Quentin},
journal={Classical and Quantum Gravity},
volume={42},
number={11},
pages={115016},
year={2025},
publisher={IOP Publishing}
}