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Lucas Barrault – TASC 9 KASC 16 workshop Collaboration: L.Bugnet, S.Mathis, J.S.G. Mombarg Exploring the probing power of -Dor’s inertial dip to core magnetism γ 1 Here!
Internal B field measurements L.Barrault -- TASC9-KASC16 workshop 2 Hatt+ 24 Where do they come from? In-situ dynamo (TS mechanism) Fossil field theory ? Hatt+ 24: significant detection of B fields in the radiative zone of 23 young RGB stars also Li+ 22,23, Deheuvels+ 23
Internal B field measurements L.Barrault -- TASC9-KASC16 workshop 3 Hatt+ 24: significant detection of B fields in the radiative zone of 23 young RGB stars also Li+ 22,23, Deheuvels+ 23 Hatt+ 24 Where do they come from? In-situ dynamo (TS mechanism) Fossil field theory ? Need to push measurements downwards in evolution: Sub-Giants and Main Sequence see J.Ballot’s talk
-Doradus γ Intermediate-mass MS : M*∈[1.5,2.0] M⊙ Radiative zone Convective core Pure inertial modes Gravito-inertial modes Ωenv ≃60Ω⊙ 4 } } Envelope probe Core probe Ω(r,θ) 4 L.Barrault -- TASC9-KASC16 workshop Dynamo generation: Origin of RGB fields?
Dynamo generation: Origin of RGB fields? -Doradus γ Intermediate-mass MS : M*∈[1.5,2.0] M⊙ Radiative zone Convective core Pure inertial modes Gravito-inertial modes Ωenv ≃60Ω⊙ 5 } } Envelope probe Core probe Ω(r,θ) 5 L.Barrault -- TASC9-KASC16 workshop Present talk: CORE “near-core” = base of the radiative envelope
The PP diagram: a window on stellar dynamics Δ For pure gravity modes ΔP = Π0= cst 6 For gravito-inertial modes, slope in the inertial frame Adapted from Van Reeth et al. 2018, KIC12066947 L.Barrault -- TASC9-KASC16 workshop
The PP diagram: a window on stellar dynamics Δ For pure gravity modes ΔP = Π0= cst 7 For gravito-inertial modes, slope in the inertial frame Adapted from Van Reeth et al. 2018, KIC12066947 L.Barrault -- TASC9-KASC16 workshop Lignières et al. 2024 Additional curvature brought by envelope magnetism for magneto-gravito-inertial modes See J. Ballot’s talk
8 Van Reeth et al. 2018, KIC12066947 Inertial dip as a probe of core dynamics L.Barrault -- TASC9-KASC16 workshop 6 major studies: Ouazzani+ 20, Saio+ 21, Tokuno & Takata 22, Galoy+ 24 Barrault+ 25a, Barrault+25b(accepted) Prograde inertial mode + prograde dipole g-i modes In a sub-inertial regime ω< 2Ω The inertial dip!
9 Van Reeth et al. 2018, KIC12066947 Van Reeth et al. 2018, KIC12066947 Inertial dip as a probe of core dynamics L.Barrault -- TASC9-KASC16 workshop Prograde inertial mode + prograde dipole g-i modes In a sub-inertial regime ω< 2Ω The inertial dip! Tokuno & Takata 2020
Results: bi-layer Alfvén frequency Increasing core field strength 16 L.Barrault -- TASC9-KASC16 workshop B−∈[0.3,30] MG Rcore B+= 50 kG Unnoticeable influence of envelope magnetism with this field configuration and intensity Barrault et al. 2025b (accepted) Ω/2π= 1.14 c . d−1 ϵ= 1.5 ×10−2 senv =2Ω ωenv Period-spacing pattern in the co-rotating frame
No significantly strong magnetic shift of the inertial dip -Uncertainties: observational + Period-Spacing Pattern building -Modeling of processes shifting the dip: Age, envelope/core rotation Threats on detectability 17 L.Barrault -- TASC9-KASC16 workshop ? B Barrault+ 25a Bowman & Michielsen 22 Ouazzani+ 20 Saio+ 21Galoy+ 24 No interaction due to g-i mode suppression Strong B field converting g-i modes in slow Alfvénic waves Fuller+ 15 Rui & Fuller 23Lecoanet+ 17,22 Can we estimate this for typical -Dor stars? γ
Threats on detectability 18 L.Barrault -- TASC9-KASC16 workshop ? No significantly strong magnetic shift of the inertial dip -Uncertainties: observational + Period-Spacing Pattern building -Modeling of processes shifting the dip: Age, envelope/core rotation B Barrault+ 25a Bowman & Michielsen 22 Ouazzani+ 20 Saio+ 21Galoy+ 24 No interaction due to g-i mode suppression Strong B field converting g-i modes in slow Alfvénic waves Fuller+ 15 Rui & Fuller 23Lecoanet+ 17,22 Can we estimate this for typical -Dor stars? γ
Yes we can… but ask me later for details 19 L.Barrault -- TASC9-KASC16 workshop ? B Barrault et al. 2025b (accepted) WITH this configuration, impossible to have a dip appearing in the Period-Spacing pattern AND a continuous field at the boundary -Magnetic shift , so easier for “moderate” rotators -Typical core fields in TAMS have more effects than on the ZAMS ∝Le = ωA 2Ω
Bi-layer Alfvén vs rotation frequency Effect of magnetism in this configuration very similar to differential rotation Increasing core rotation 20 L.Barrault -- TASC9-KASC16 workshop Increasing core field strength Barrault et al. 2025b (accepted) Barrault et al. 2025a Magnetism Differential rotation
Disentangling core rotation and magnetism 21 L.Barrault -- TASC9-KASC16 workshop -Educated guesses on the field strength vs differential rotation ratio: -Integrating different azimuthal orders m: strong B, low differential rotation vs low B, strong differential rotation As for mixed p-g modes in RGB: B field effects Rotation effects ∝m2 ∝m Barrault et al. 2025b (accepted) Barrault et al. 2025a Galoy et al. 2024 We only have m=-1 for now!
Evolution of the dip spin parameter with internal processes 22 L.Barrault -- TASC9-KASC16 workshop “Outliers” in the distribution of differential rotation detected by the shift of the dip What if core magnetism was shifting it as well? Saio+ 21 Barrault et al. 2025b (accepted)
Evolution of the dip spin parameter with internal processes 23 L.Barrault -- TASC9-KASC16 workshop “Outliers” in the distribution of differential rotation detected by the shift of the dip What if core magnetism was shifting it as well? Saio+ 21 Bφ 0|Rcore/2 ≈2.8 MG Bφ 0|Rcore/2 ≈3.3 MG In this particular configuration, would require field at the MG scale Only a crude estimate, further studies are required for a detection Barrault et al. 2025b (accepted)
•Inertial dips: a unique way of accessing core magnetism 24 Conclusion & Perspectives L.Barrault -- TASC9-KASC16 workshop •Magnetic shift of the inertial dip in a toroidal config •Best targets: moderate rotation, aged -Dor γ •Future numerical works on the effect of more realistic magnetic configurations on core modes
25 Thank you very much And thanks to our dear EU And check this for the latest news of our group here! (and our paper)
