Atelier API "Ondes gravitationnelles et objets compacts"

Session

Contributed talks

10 déc. 2025, 13:20

Bâtiment 18 - Salle 204 (Observatoire de Paris - site de Meudon)

9. Results and current activities of the Multimessenger observations Division of the Einstein Telescope Observing Science Board

Susanna Diana VERGANI (CNRS-Observatoire de Paris)

10/12/2025 13:20

Results of the Multimessenger observations Division of the Einstein Telescope Observing Science Board

The Einstein Telescope is the European Next Generation gravitational wave (GW) interferometer. Despite the fact that it will be operational from the late 2030’s, its revolutionary capabilities require that the preparation of the multimessenger follow-up of the GW events (in terms of useful...

10. The SVOM Core Program : first results

Susanna Diana VERGANI (CNRS-Observatoire de Paris)

10/12/2025 13:40

SVOM (Space-based multi-band astronomical Variable Objects Monitor) is a Sino-French mission launched in June 2024. Its Core Program is dedicated to the detection and study of Gamma-Ray Bursts (GRBs). I will show how the set of SVOM instruments as well as the observing strategy compare with previous mission, present the first results and show the new questions they are opening on the study of GRBs.

1. From the accretion processes to the electromagnetic signatures of supermassive binary black holes

Raphaël Mignon-Risse (CNRS/LAM)

10/12/2025 16:30

Despite the re-birth of multi-messenger astronomy, no unambiguous electromagnetic (EM) counterpart to binary black hole (BBH) pre-/post-merger has been reported. Indeed, stellar-mass BBHs are expected to be gas-poor ; however, this should not be the case of supermassive BBHs, whose GWs will be detectable with LISA (2035+). Detecting the EM pre-merger counterpart would allow for optimal...

8. Multi-messenger observations of binary neutron star mergers: synergies between the next generation gravitational wave interferometers and wide-field, high-multiplex spectroscopic facilities

Sofia Bisero (IRFU, CEA Paris-Saclay)

10/12/2025 17:00

Next generation gravitational wave (GW) interferometers such as the Einstein Telescope (ET) will explore a significantly larger volume of the Universe, detecting up to 10$^{5}$ binary neutron star system mergers (BNS) per year beyond the Local Universe. Identifying the faint optical-NIR electromagnetic (EM) counterparts of these GW signals within vast sky localization regions, among a huge...

14. Testing planar matter distributions at the GC

Arianna Foschi (Observatoire de Meudon)

11/12/2025 11:25

The surroundings of the supermassive black hole at the center of our galaxy, Sagittarius A*, are mostly unknown and for this reason many studies have tried to constrain the presence of an extended mass around it, with the aim of simulating either dark matter distribution or stellar clusters. However, all these works focus on spherically symmetric distributions of matter, while observations...

4. Detectability of the spin parameters of SgrA* using multiple S stars

Karim Abd El Dayem (Observatoire de Paris (LESIA))

11/12/2025 11:55

Context. The orbits of S stars around the Galactic Center black hole, Sgr A*, offer a unique opportunity to probe the relativistic regime of gravity and test the no-hair theorem. While the Schwarzschild precession has been detected with S2, the detection of spin-induced (Kerr) effects—Lense–Thirring and quadrupole moment terms—remains a major observational challenge.
Aims. We aim to quantify...

3. The Supermassive Black Hole Binary Candidate 3C 66A

Paloma Thevenet (Observatoire de Paris)

11/12/2025 12:25

The blazar 3C 66A is known for its optical flux periodicity and complex jet kinematics. Using 22/43 GHz KaVa (KVN and VERA array) observations and 43 GHz VLBA (Very Long Baseline Array) archival data, we have found that its pc-scale jet has a twisted structure and that the inner jet undergoes periodic swings every 13 years. In this talk, we will describe the peculiar characteristics of 3C 66A...

11. Gravitational scattering of solitonic boson stars: Analytics vs Numerics

Tamanna Jain (LPENS)

12/12/2025 09:30

We study the scattering of boson-star binaries, taking into account
three effects: point-mass gravitational, tidal, and short-range
scalar-field interactions. We compare analytic results to the
scattering angle extracted from four sequences of numerical-relativity
simulations at fixed energy and varying impact parameter. The
very good agreement exhibits the attractive (repulsive)
effect...

7. Dynamics of Spinning, Eccentric Binary Black Holes at Second Post-Newtonian Order

Tom Colin (LUX)

12/12/2025 11:10

We present an analytical solution for the dynamics of spinning binary black holes on eccentric orbits at second post-Newtonian (2PN) order, extending the 1.5PN results of Cho and Lee. For the orbital angular momentum L and the individual spins S1 and S2, we exploit the separation of timescales between orbital motion and precession to construct a hybrid solution that combines the...

2. Beyond circles: stationary axisymmetric black holes and the breaking of circularity

Jacopo MAZZA (IJCLab)

12/12/2025 11:40

Circularity is an accidental symmetry of the Kerr metric, one that is widely assumed when searching for rotating black hole solutions in modified gravity as well as when constructing models of Kerr mimickers. Though extremely enticing, circularity is often an excessively restrictive assumption, and understanding the consequences of its loss is thus crucially relevant. In this seminar, I wish...

5. Slowly rotating black holes in scalar-tensor theories of gravity

Hugo Candan (LUTH, Observatoire de Paris PSL & IJCLab, Université Paris-Saclay)

12/12/2025 12:10

We are entering an era of high-precision measurements of black holes, either through gravitational waves (LVK, and soon LISA) or direct imaging (EHT). It is therefore interesting to study black hole spacetimes within both General Relativity (GR) and alternative theories, to confront them with observations. In GR, the Kerr spacetime, which describes rotating black holes, is the most general...

15. Dynamical tidal response of Schwarzschild black holes

Oscar Combaluzier--Szteinsznaider (APC (Astroparticules et Cosmologie))

12/12/2025 14:50

The response of a black hole to an external tidal field is encapsulated in the so-called Love numbers. While these are well known in the context of static and linear perturbations, future developments of gravitational-wave astronomy will require more precise results, taking subleading effects into account.

In the talk, I will show how to compute the response of a Schwarzschild black hole to...