@article{22262, abstract = {Mixed modes are observed in many low-mass evolved stars. They provide information about core rotation rates of these stars, which are lower than predicted by stellar evolution models. The mixed modes themselves have been invoked as an angular momentum (AM) transport mechanism, but estimating their transport efficiency requires knowledge of their amplitudes. We constrain, for the first time, the mixed-mode amplitudes in 2D hydrodynamical simulations of a 1.3M⊙ red giant using the code MUSIC. We perform two simulations with outer radial truncations at fractional radii ro/r⋆ = 0.90 and 0.98. We compare the modes in the simulation with those found using both GYRE and a Dedalus eigenvalue solver. Excellent frequency agreement is found for all p-dominated modes, with minor discrepancies for g-dominated modes, especially in the frequency range [60, 240] μHz. We find excellent eigenfunction agreement for all modes except those in this frequency range. According to empirical predictions, the largest kinetic energies are located around Vmax= 312.μHz, but in both simulations, the modes with frequencies of ν < 50 μHz have the largest kinetic energies. In the simulation with r/r⋆ = 0.98, the simulated modes have extrapolated surface velocities comparable to the empirical predictions, with the highest surface velocities in a bell-shaped curve peaking around ν = 700 μHz. The extrapolated surface velocities of the low-frequency modes are small and thus hard to observe, but their large kinetic energies deeper in the interior could significantly impact AM transport, which has not yet been investigated.}, author = {De Vries, Nils B. and Le Saux, Arthur and Baraffe, Isabelle and Guillet, Thomas and Townsend, Richard H.D. and Leclerc, Armand and Morison, Adrien}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Stellar physics, Stellar interiors, Asteroseismology, Stellar oscillations, Hydrodynamical simulations}, number = {2}, publisher = {IOP Publishing}, title = {{Revealing mixed modes in compressible hydrodynamical simulations of red giant stars}}, doi = {10.3847/1538-4357/ae7a3c}, volume = {1005}, year = {2026}, } @article{22663, abstract = {The detection of strong, large-scale magnetic fields at the surfaces of the oldest white dwarfs might point toward a hidden internal magnetic field slowly rising to the surface. In addition, strong magnetic fields have recently been measured through asteroseismology in the radiative interiors of red giant stars, the progenitors of white dwarfs. To investigate the potential connection between these observations, we revisited the fossil field framework using asteroseismic detections to constrain the strength of such magnetic fields as red giants evolve into the white dwarf stage. We assumed that the magnetic field was either created during the core convection on the main sequence or that it fills the radiative interior as the star evolves on the red giant branch. From these initial conditions, we evolved the magnetic flux, allowing for magnetic diffusion along the evolution of a modeled 1.5 M⊙ star. We find that measured field strengths in red giants attributed to the hydrogen-burning shell are compatible with the field amplitudes and emergence timescales of magnetized white dwarfs. On the contrary, magnetic fields generated solely from a convective-core dynamo on the main sequence and detectable on the red giant branch would be buried too deep in the star and would not match the breakout timescales or the field strengths of magnetic white dwarfs. Therefore, for us to connect magnetic fields observed along the late evolution of stars via a fossil field we would need to find a broadly magnetized internal radiative zone on the red giant branch.}, author = {Einramhof, Lukas and Bugnet, Lisa Annabelle and Calcaferro, L. M. and Barrault, Lucas and Das, S. B.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, publisher = {EDP Sciences}, title = {{Magneto-archeology of white dwarfs}}, doi = {10.1051/0004-6361/202659069}, volume = {708}, year = {2026}, } @article{21659, abstract = {The recent detection of solar equatorial Rossby waves has renewed interest in the study of gravito-inertial waves propagating in the convective envelope of solar-type stars. In particular, the ability of these envelope gravito-inertial modes to couple with those trapped in the radiative interior could open up new opportunities for probing the deep-layer dynamics of solar-type stars. The possibility for such a coupling to occur is particularly favoured among pre-main-sequence (PMS) solar-type stars. Indeed, due to the contraction of the protostellar object, they are able to reach high rotation frequencies before nuclear reactions are ignited and magnetic braking becomes the driving mechanism for their rotational evolution. In this work, we studied the coupling between the envelope inertial waves and the radiative interior g modes in PMS stars, focussing on the case of prograde dipolar modes. We considered the cases of 0.5 M⊙ and 1 M⊙ PMS models, each with three different scenarios of rotational evolution. We show that for stars that have formed with a sufficient amount of angular momentum, this coupling can occur in frequency ranges that are accessible to space-borne photometry, creating inertial dips in the period spacing pattern. Using an asymptotic analysis, we characterised the shape of these inertial dips to show that they depend on rotation and on the stiffness of the convective-radiative interface.}, author = {Breton, S. N. and Pezzotti, C. and Mathis, S. and Bugnet, Lisa Annabelle and Di Mauro, M. P. and Joergensen, J. and Zwintz, K. and Lanza, A. F.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, publisher = {EDP Sciences}, title = {{Core-envelope coupling of gravito-inertial waves in pre-main-sequence solar-type stars}}, doi = {10.1051/0004-6361/202659309}, volume = {707}, year = {2026}, } @article{23047, abstract = {Aims. We investigate signatures of pressure extrema on global oscillations in discs. Methods. We used the framework of wave topology to establish a generalised local dispersion relation that includes pressure gradients. We highlight the influence of a previously unrecognised epicyclic–acoustic frequency, and we derive an analytical criterion for the existence of a branch of modes transiting between the inertial and the pressure bands, known as topological modes. Results. We find that pressure extrema consist of wave guides in which such topological modes propagate. The fundamental mode trapped at a pressure bump can propagate at any frequency, allowing it to resonate with any temporal forcing. Conversely, the fundamental mode associated with a pressure dip propagates at any vertical phase velocity. These specific features make them attractive candidates for future discoseismology.}, author = {Leclerc, Armand and Laibe, Guillaume and Lynch, Elliot and Perez, Nicolas}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {accretion, accretion disks, hydrodynamics, instabilities, waves, protoplanetary disks}, publisher = {EDP Sciences}, title = {{Radial modes of pressure bumps and dips in astrophysical discs}}, doi = {10.1051/0004-6361/202558428}, volume = {708}, year = {2026}, } @article{19283, abstract = {Context. The presence of dips in the gravity mode period spacing versus period diagram of γ Doradus stars is now well established thanks to recent asteroseismic studies. Such Lorentzian-shaped inertial dips arise from the interaction of gravito-inertial modes in the radiative envelope of intermediate-mass main sequence stars with pure inertial modes in their convective core, and allow us to study stellar internal properties. This window onto stellar internal dynamics is extremely valuable in the context of the understanding of angular-momentum transport inside stars, as it allows us to probe rotation in their core. Aims. We investigate the signature and the detectability of a differential rotation between the convective core and the near-core region inside γ Doradus stars from the properties of inertial dips. Methods. We studied the coupling between gravito-inertial modes in the radiative zone and pure inertial modes in the convective core in the sub-inertial regime, allowing for a two-zone differential rotation from the two sides of the core-to-envelope boundary. We solved the coupling equation numerically and matched the result to an analytical derivation of the Lorentzian dip properties. We then used typical values of measured near-core rotation and buoyancy travel time to infer ranges of parameters for which differential core to near-core rotation would be detectable in current Kepler data. Results. We show that increasing the convective core rotation with respect to the near-core rotation leads to a shift of the period of the observed dip to lower periods. In addition, the dip gets deeper and thinner as the convective core rotation increases. We demonstrate that such a signature is detectable in Kepler data, given appropriate dip-parameter ranges and near-core structural properties. Conclusions. Studying the dip properties in asteroseismic data thus allows us to access core to near-core radial differential rotation and to better understand the transport of angular momentum at convective–radiative interfaces in intermediate-mass main sequence stars.}, author = {Barrault, Lucas and Mathis, S. and Bugnet, Lisa Annabelle}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, publisher = {EDP Sciences}, title = {{Constraining differential rotation in γ Doradus stars from the properties of inertial dips}}, doi = {10.1051/0004-6361/202451541}, volume = {694}, year = {2025}, } @article{20350, abstract = {Context. Rotation plays an important role in stellar evolution. However, the mechanisms behind the transport of angular momentum in stars at various stages of their evolution are not well understood. To improve our understanding of these processes, it is necessary to measure and validate the internal rotation profiles of stars across different stages of evolution and mass regimes. Aims. Our aim is to constrain the internal rotation profile of the 12-M⊙ β Cep pulsator HD 192575 from the observed pulsational multiplets and the asymmetries of their component frequencies. Methods. We updated the forward asteroseismic modelling of HD 192575 based on new TESS observations. We inverted the rotation profile from the symmetric part of the splittings and computed the multiplet asymmetries due to the Coriolis force and stellar deformation, which we treated perturbatively. We compared the computed asymmetries with the observed asymmetries. Results. Our new forward asteroseismic modelling is in agreement with previous results but with increased uncertainties, partially due to increased frequency precision, which required us to relax certain constraints. Ambiguity in the mode identification is the main source of the uncertainty, which also affects the inferred rotation profiles. Almost all acceptable rotation profiles occur in the regime below 0.4 d−1 and favour weak radial differential rotation, with a ratio of core to envelope rotation of less than 2. We find that the quality of the match between the observed and theoretically predicted mode asymmetries is strongly dependent on the mode identification and the internal structure of the star. Conclusions. Our results offer the first detailed rotation inversion for a β Cep pulsator. They show that the rotation profile and the mode asymmetries provide a valuable tool for further constraining the evolutionary properties of HD 192575, and in particular the details of angular momentum transport in massive stars.}, author = {Vanlaer, V. and Bowman, D. M. and Burssens, S. and Das, Srijan B and Bugnet, Lisa Annabelle and Mathis, S. and Aerts, C.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, publisher = {EDP Sciences}, title = {{Interior rotation modelling of the β Cep pulsator HD 192575 including multiplet asymmetries}}, doi = {10.1051/0004-6361/202452885}, volume = {701}, year = {2025}, } @article{20454, abstract = {Context. γ Dor stars are ideal targets for studies of the innermost dynamical properties of stars, due to their rich asteroseismic spectrum of gravity modes. Integrating internal magnetism to the picture appears as the next milestone of detailed asteroseismic studies, for its prime importance on stellar evolution. The inertial dip in prograde dipole modes period-spacing pattern of γ Dors stands out as a unique window on the convective core structure and dynamics. Recent studies have highlighted the dependence of the dip structure on core density stratification, the contrast of the near-core Brunt-Väisälä frequency and rotation rate, as well as the core-to-near-core differential rotation. In addition, the effect of envelope magnetism has been derived on low-frequency magneto-gravito-inertial waves. Aims. We revisited the inertial dip formation including core and envelope magnetism, and explored the probing power of this feature on dynamo-generated core fields. Methods. We considered as a first step a toroidal magnetic field with a bi-layer (core and envelope) Alfvén frequency. This configuration allowed us to revisit the coupling problem using our knowledge on both core magneto-inertial modes and envelope magneto-gravito-inertial modes. Using this configuration, we were able to stay in an analytical framework to exhibit the magnetic effects on the inertial dip shape and location. This configuration allowed a laboratory to be set up that moves us towards the comprehension of magnetic effects on the dip structure. Results. We show a shift of the inertial dip towards lower spin parameter values and a thinner dip with increasing core magnetic field’s strength, quite similar to the signature of differential rotation. The magnetic effects become sizeable when the ratio of the magnetic to the Coriolis effects is high enough. We explored the potential degeneracy of the magnetic effects with differential rotation. We studied the detectability of core magnetism, considering both observational constraints on the periods of the modes and potential gravito-inertial mode suppression.}, author = {Barrault, Lucas and Bugnet, Lisa Annabelle and Mathis, S. and Mombarg, J. S.G.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, publisher = {EDP Sciences}, title = {{Exploring the probing power of γ Dor's inertial dip for core magnetism: The case of a toroidal field}}, doi = {10.1051/0004-6361/202555213}, volume = {701}, year = {2025}, } @article{20931, abstract = {Context. Asymmetries in the observed rotational splittings of a multiplet contain information about the star’s rotation profile and internal magnetic field. Moreover, the frequency regularities of multiplets can be used for mode identification. However, to exploit this information, highly accurate theoretical predictions are needed. Aims. We aim to quantify the difference in the predicted mode asymmetries between a 1D perturbative method and a 2D method that includes a 2D stellar structure model, which takes rotation into account. We then place these differences between 1D and 2D methods in the context of asteroseismic measurements of internal magnetic fields. We only focus on the asymmetries and not on possible additional frequency peaks that can arise when the magnetic and rotation axis are misaligned. Methods. We coupled the 1D pulsation codes GYRE and StORM to the 2D stellar structure code ESTER and compared the oscillation predictions with the results from the 2D TOP pulsation code. We focused on zero-age main-sequence models representative of rotating β Cephei pulsators spinning at up to 20 per cent of the critical Keplerian rotation rate. Specifically, we investigated low-radial-order gravity and pressure modes. Results. We find a generally good agreement between the oscillation frequencies resulting from the 1D and 2D pulsation codes. We report differences in predicted mode multiplet asymmetries of mostly below 0.06 d−1. Since the magnetic asymmetries are small compared to the differences in the rotational asymmetries resulting from the 1D and 2D predictions, accurate measurements of the magnetic field are in most cases challenging. Conclusions. Differences in the predicted mode asymmetries of a rotating star between 1D perturbative methods and 2D non-perturbative methods can greatly hinder accurate measurements of internal magnetic fields in main-sequence pulsators with low-order modes. Nevertheless, reasonably accurate measurements could be possible with npg ≥ 2 modes if the internal rotation is roughly below 10 per cent of the Keplerian critical rotation frequency for (aligned) magnetic fields of the order of a few hundred kilogauss. While the differences between the 1D and 2D frequency predictions are mostly too large for internal magnetic field detections, the rotational asymmetries predicted by StORM are in general accurate enough for asteroseismic modelling of the stellar rotation in main-sequence stars with identified low-order modes.}, author = {Mombarg, J. S.G. and Vanlaer, V. and Das, Srijan B and Rieutord, M. and Aerts, C. and Bugnet, Lisa Annabelle and Mathis, S. and Reese, D. R. and Ballot, J.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, publisher = {EDP Sciences}, title = {{Is a 1D perturbative method sufficient for asteroseismic modelling of β Cephei pulsators? Implications for measurements of rotation and internal magnetic fields}}, doi = {10.1051/0004-6361/202557247}, volume = {704}, year = {2025}, }