arXiv subjects

Emmanuel Gianuzzi

Publications and source records attributed to Emmanuel Gianuzzi.

4 recordsLinked to original sources

arXiv2026

Stability of circumbinary planets: the role of binary properties and migration scenarios

Among the thousands of exoplanets detected to date, only a very small fraction are classified as circumbinary planets, and this number becomes negligible when considering low-mass planets. This rarity may partly result from observational biases, but also from the challenging dynamical environment of binary systems, which can prevent the long-term stability of planetary orbits. It is therefore essential to investigate the conditions that enable the formation and survival of stable circumbinary planets, particularly in the low-mass regime. To this end, we performed N-body simulations coupled with a planet migration prescription to study the post-formation dynamics of two 10 Earth-mass circumbinary planets in a protoplanetary disc. Based on more than 1,000 simulations, we find that inward migration can, in some cases, be halted through resonance capture with the binary. In contrast to some previous purely N-body studies, these configurations appear to remain stable over long timescales. We further find that the binary mass ratio $q_B$ and eccentricity $e_B$ strongly influence the stability of multi-planet systems. Within the explored parameter space, some regions support long-term stability, whereas others are highly unstable. These stability regions are also sensitive to the migration timescales, and therefore to disc properties and planetary masses. Finally, our simulations suggest that systems in which two planets enter resonance while migrating together are more likely to form stable multi-planet configurations, particularly around highly eccentric binaries. These results provide a first step toward identifying binary star systems that are most promising for hosting multiple low-mass circumbinary planets.

astro-ph.EP↗

arXiv2026

Circumbinary planets in coplanar triple-star systems: I. Minimum eccentricity variation region

We aim to determine the conditions under which Lidov-Kozai oscillations can arise for circumbinary planets in hierarchical triple-star systems, and to identify the orbital regions where competing secular perturbations minimize eccentricity excitation. We analyzed the statistical properties of hierarchical triples from the Multiple Star Catalog to construct representative synthetic configurations. We then performed N-body simulations of circumbinary planets embedded in these systems, systematically exploring their orbital evolution and long-term stability across a range of semimajor axes and inclinations. For representative compact hierarchical triple-star systems with masses $m_0 \sim m_1 \approx 0.75\,{\rm M}_\odot$ and $m_2 \approx 0.6\,{\rm M}_\odot$ and eccentricities $e_1 \sim 0.1$ and $e_2 \sim 0.4$, dynamically significant stable circumbinary regions exist only in sufficiently hierarchical configurations, with period ratios $P_2 /P_1 \gtrsim 10^2$. In this regime, the secular competition between the tertiary perturbations and the apsidal precession induced by the compact inner binary determines both the onset of Lidov-Kozai oscillations beyond a critical distance ($a_{\rm LK}$) and the location of a region where eccentricity variations are minimized, i.e., the minimum eccentricity variation region (MER). We derived analytical estimates for these dynamical features, showing that the MER is well described by the analytical quantity $a_{\rm short}$ on short and intermediate timescales, while on secular timescales it converges toward the equilibrium prediction $a_{\rm ME}$. These analytical estimates agree well with N-body simulations. Application to the observed triple system WDS 08403+1921 confirms that $a_{\rm LK}$ and $a_{\rm ME}$ accurately identify the main dynamical features of the stability map.

astro-ph.EP↗

arXiv2024

Unveiling hidden companions in post-common-envelope binaries: A robust strategy and uncertainty exploration

Some post-common-envelope binaries are binary stars with short periods that exhibit significant period variations over long observational time spans. These eclipse timing variations (ETVs) are most likely to be accounted for by the presence of an unseen massive companion, potentially of planetary or substellar nature, and the light-travel time (LTT) effect. In this study, our main objective is to describe the diversity of compatible nontransit companions around PCEBs and explore the robustness of the solutions by employing tools for uncertainty estimation. We select the controversial data of the QS Vir binary star, which previous studies have suggested hosts a planet. We employ a minimizing strategy, using genetic algorithms to explore the global parameter space followed by refinement of the solution using the simplex method. We evaluate errors through the classical MCMC approach and discuss the error range for parameters. Our results highlight the strong dependence of ETV models for close binaries on the dataset used, which leads to relatively loose constraints on the parameters of the unseen companion. We find that the shape of the $O-C$ curve is influenced by the dataset employed. We propose an alternative method to evaluate errors on the orbital fits based on a grid search surrounding the best-fit values, obtaining a wider range of plausible solutions that are compatible with goodness-of-fit statistics. We also analyze how the parameter solutions are affected by the choice of the dataset, and find that this system continuously changes the compatible solutions as new data are obtained from eclipses. The best-fit parameters for QS Vir correspond to a low-mass stellar companion (57.71 $M_{jup}$ ranging from 40 to 64 $M_{jup}$) on an eccentric orbit ($e=0.91^{+0.07}_{-0.17}$) with a variety of potential periods ($P = 16.69 ^{+0.47}_{-0.42}$ yr.)

astro-ph.SR↗

arXiv2022

Circumbinary planets: migration, trapping in mean-motion resonances, and ejection

Most of the planetary systems discovered around binary stars are located at approximately three semi-major axes from the barycentre of their system, curiously close to low-order mean-motion resonances (MMRs). The formation mechanism of these circumbinary planets is not yet fully understood. In situ formation is extremely challenging because of the strong interaction with the binary. One possible explanation is that, after their formation, the interactions between these planets and the surrounding protoplanetary disc cause them to migrate at velocities dependent on the nature of the disc and the mass of the exoplanet. Although extensive data can be obtained with direct hydrodynamical simulations, their computational cost remains too high. On the other hand, the direct n-body simulations approach allows us to model a large variety of parameters at much lower cost. We analyse the planetary migration around a wide variety of binary stars using Stokes-like forces that mimic planetary migration at a constant rate. Our goal is to identify the main parameters responsible for the ejection of planets at different resonances with the inner binary. We performed 4200 n-body simulations with Stokes-like forces and analysed their evolution and outcome as a function of the properties of each system. For each simulated exoplanet, we applied an ensemble learning method for classification in order to clarify the relationship between the inspected parameters and the process of MMR capture. We identify the capture probability for different N/1 MMRs, 4/1 being the most prone to capture exoplanets, with 37% probability, followed by MMR 5/1 with $\sim$ 23% of probability. The eccentricity of the binary is found to be the most important parameter in determining the MMR capture of each circumbinary exoplanet, followed by the mass ratio of the binary and the initial eccentricity of the planet.

astro-ph.EP↗