Gravitational-wave detection and parameter estimation for accreting black-hole binaries and their electromagnetic counterpart

Andrea Caputo , Laura Sberna , Alexandre Toubiana (1, 2) , Stanislav Babak (1) , Enrico Barausse (2) , Sylvain Marsat (1) , Paolo Pani

1 APC (UMR_7164) - AstroParticule et Cosmologie
2 IAP - Institut d'Astrophysique de Paris

We study the impact of gas accretion on the orbital evolution of black-hole binaries initially at large separation in the band of the planned Laser Interferometer Space Antenna (LISA). We focus on two sources: (i)~stellar-origin black-hole binaries~(SOBHBs) that can migrate from the LISA band to the band of ground-based gravitational-wave observatories within weeks/months; and (ii) intermediate-mass black-hole binaries~(IMBHBs) in the LISA band only. Because of the large number of observable gravitational-wave cycles, the phase evolution of these systems needs to be modeled to great accuracy to avoid biasing the estimation of the source parameters. Accretion affects the gravitational-wave phase at negative ($-4$) post-Newtonian order, and is therefore dominant for binaries at large separations. If accretion takes place at the Eddington or at super-Eddington rate, it will leave a detectable imprint on the dynamics of SOBHBs. In optimistic astrophysical scenarios, a multiwavelength strategy with LISA and a ground-based interferometer can detect about $10$ (a few) SOBHB events for which the accretion rate can be measured at $50\%$ ($10\%$) level. In all cases the sky position can be identified within much less than $0.4\,{\rm deg}^2$ uncertainty. Likewise, accretion at $\gtrsim 10\%$ ($\gtrsim 100\%$) of the Eddington rate can be measured in IMBHBs up to redshift $z\approx 0.1$ ($z\approx 0.5$), and the position of these sources can be identified within less than $0.01\,{\rm deg}^2$ uncertainty. Altogether, a detection of SOBHBs or IMBHBs would allow for targeted searches of electromagnetic counterparts to black-hole mergers in gas-rich environments with future X-ray detectors (such as Athena) and radio observatories (such as SKA).

Mots clés: black hole: binary; black hole: accretion; binary: coalescence; gas: accretion; X-ray: detector; LISA; gravitational radiation; electromagnetic field: production; gravitational radiation detector; observatory; interferometer; numerical calculations; statistical analysis; gravitational radiation: direct detection; gravitational radiation: emission; gravitation: weak field

Domaines: Astrophysique [astro-ph]; Relativité Générale et Cosmologie Quantique [gr-qc]

Andrea Caputo, Laura Sberna, Alexandre Toubiana, Stanislav Babak, Enrico Barausse, et al.. Gravitational-wave detection and parameter estimation for accreting black-hole binaries and their electromagnetic counterpart. Astrophys.J., 2020, 892 (2), pp.90. ⟨10.3847/1538-4357/ab7b66⟩. ⟨hal-02483942⟩