Stellar deformations play a significant role in the dynamical evolution of stars in binary systems, impacting the tidal dissipation and the outcomes of mass transfer processes. The prevalent method for modelling the deformations and tidal interactions of celestial bodies solely relies on the perturbative approach, which assumes that stellar deformations are minor perturbations to the spherical symmetry. An observable consequence of stellar deformations is the apsidal motion in eccentric systems. Our objective is to assert the reliability of the perturbative approach when applied to close and strongly deformed binary systems. We have developed a non-perturbative 3D modelling method designed to account for high stellar deformations to explore the limitations of the perturbative models. Our research highlights that the perturbative model becomes imprecise and underestimates the tidal force and rate of apsidal motion at a short orbital separation. This discrepancy primarily results from the first-order treatment in the perturbative approach, and cannot be rectified using straightforward mathematical corrections due to the strong non-linearity and numerous parameters of the problem. We have determined that our methodology affects the modelling of approximately 42% of observed binary systems with measured apsidal motion, introducing a discrepancy greater than 2% when the normalised orbital separation verifies q^(-1/5)a(1-e^2)/R1 < 6.5. The perturbative approach underestimates tidal interactions between bodies up to ~40% for close low-mass binaries. All the subsequent modelling is impacted by our findings, in particular, the tidal dissipation is significantly underestimated. As a result, all binary stellar models are imprecise when applied to systems with a low orbital separation, and the outcomes of these models are also affected by these inaccuracies.
Theoretical tidal evolution constants for stellar models from the pre-main sequence to the white dwarf stage Apsidal motion constants, moment of inertia, and gravitational potential energy
Quasi-stationary tidal evolution with arbitrarily misaligned orbital and stellar angular momenta with a preliminary numerical investigation in the non-dissipative limit
The Beauty of k2: Probing Stellar Interiors Using Apsidal Motion. I. The Benchmark Massive Binary HD 152248
University of Geneva（日内瓦大学）；Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut（海德堡大学天文学中心，天文计算研究所）；Keele University（基尔大学）；Kavli IPMU (WPI), The University of Tokyo（东京大学 Kavli 宇宙粒子与宇宙学前沿研究中心（WPI））
On the origin of anomalous dissipation in simulations of tidal disruption events
School of Physics and Astronomy, University of Leeds（利兹大学物理与天文学院）；Department of Physics, Syracuse University（锡拉丘兹大学物理系）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体科学系）
