arXiv subjects

Louis Manchon

Publications and source records attributed to Louis Manchon.

3 recordsLinked to original sources

arXiv2026

Probing magnetic fields in stars: A 2D oscillation framework including rotation and magnetism

Understanding the role of internal magnetic fields in stars remains a major challenge for the description of angular momentum transport and stellar evolution. It is therefore essential to probe these magnetic fields within the star, and asteroseismology provides a powerful means to do so. In this work, we present a new implementation of the 2D oscillation code ( ), which incorporates the effects of both stellar rotation and magnetic fields. Adaptive Code of Oscillations towards Realistic modeling The code has been rendered modular, making it possible to specify the set of equations to solve and the assumptions through a symbolic calculus approach. The full set of adiabatic, non-radial pulsation equations is solved using a spectral approach for the angular part of the modes and high-order finite differences for the radial part. As a first step, we focus on a magnetic field that is purely toroidal and axisymmetric about the star's rotation axis. The numerical results are compared against first-order perturbative predictions in the weak-field regime and with the traditional approximation of rotation and magnetism (TARM) in the case of stronger magnetic fields. We validate this new implementation of against perturbative and TARM approaches, showing good agreement and demonstrating the robustness of the code. The breakdown of these methods provides general validity limits. We show that internal magnetic fields leave signatures in the period spacing of g modes. These features provide a promising seismic diagnostic to probe deep stellar magnetism in {\gamma} Dor stars. Future work will aim to extend this framework to more realistic magnetic field topologies and a broader range of pulsating stars, including red giants.

astro-ph.SR↗

arXiv2026

Water gas discs in exo-asteroid belts

Observations of tens of secondary CO gas discs associated with cold exo-Kuiper belts together with other arguments have led Kral et al (2024) to propose that water ice could also sublimate in exo-asteroid belts, suggesting a new pathway for the delivery of water to terrestrial planets, including Earth. We aim to model such water vapour discs and to characterise their physical properties across a range of extrasolar systems with different host stars. We further investigate the implications for the accretion of this water by potential planets located in the inner regions of these systems. We adapt and extend the model of Kral et al (2024) to follow the outgassing, photodissociation, and viscous evolution of water vapour discs. We perform a suite of simulations exploring the parameter space, focusing on the stellar mass, the mass of the parent belt, and its orbital location. We additionally include an inner planet to estimate the mass of water accreted as a function of disc properties and system architecture. We find that systems hosting Sun's mass (and higher) stars produce water vapour very efficiently, sublimating nearly all of the ice initially present in the belt. In most cases, the bulk of the gas mass is generated early, when the stellar luminosity is highest. The amount of water accreted by inner planets can approach the initial ice mass of the belt, leading to planets with water inventories comparable to or exceeding those of Earth, potentially creating ocean planets. We find that water outgassing occurs early after the protoplanetary disc dissipates in systems containing exo-asteroid belts. ALMA, JWST and ELT are capable of detecting this water vapour for several tens of millions of years, even in relatively low-mass water discs. Hence, if such water gas discs are present, they should be detectable with current facilities.

astro-ph.EP↗

arXiv2025

The impact of the transport of chemicals and electronic screening on helioseismic and neutrino observations in solar models

The transport of chemical elements in stellar interiors is one of the greatest sources of uncertainties of solar and stellar modelling. The Sun, with its exquisite spectroscopic, helioseismic and neutrino observations, offers a prime environment to test the prescriptions used for both microscopic and macroscopic transport processes. We study in detail the impact of various formalisms for atomic diffusion on helioseismic constraints in both CLES (Scuflaire et al., 2008a) and Cesam2k2 (Morel and Lebreton 2008; Marques et al. 2013; Deal et al. 2018) models and compare both codes in detail. Moreover, due to the inability of standard models using microscopic diffusion to reproduce light element depletion in the Sun (Li, Be), another efficient process must be included to reproduce these constraints (rotation-induced: Eggenberger et al. 2022, overshooting -- or penetrative convection -- below the convective envelope: Th\'evenin et al. 2017, or ad hoc turbulence: Lebreton and Maeder 1987; Richer, Michaud, and Turcotte 2000). However, introducing such an extra mixing leads to issues with the CNO neutrino fluxes (see Buldgen et al. 2023), which seem to be systematically lower than the Borexino observations (Appel et al., 2022. Another key aspect to consider when reconciling models with neutrino fluxes is the impact of electronic screening (Mussack and D\"appen, 2011).

astro-ph.SR↗