Unveiling complex magnetic field configurations in red giant stars

Abstract

Recent measurements of magnetic field strength inside the radiative interior of red giant stars open the way towards the characterization of the geometry of stable large-scale magnetic fields. However, current measurements do not properly constrain the topology of magnetic fields due to degeneracies on the observed magnetic field signature on such $\ell =1$ mode frequencies. Efforts focused towards unambiguous detections of magnetic field configurations are now key to better understand angular momentum transport in stars. We investigate the detectability of complex magnetic field topologies inside the radiative interior of red giants. We focus on a field composed of a combination of a dipole and a quadrupole (quadrudipole), and on an offset field. We explore the potential of probing such magnetic field topologies from a combined measurement of magnetic signatures on $\ell =1$ and quadrupolar ($\ell =2$) mixed mode oscillation frequencies. We first derive the asymptotic theoretical formalism for computing the asymmetric signature in frequency pattern for $\ell =2$ modes due to a quadrudipole magnetic field. The degeneracy of the quadrudipole with a dipole is lifted when considering both $\ell =1$ and $\ell =2$ mode frequencies. In addition to the analytical derivation for the quadrudipole, we present the prospect for complex magnetic field inversions using magnetic sensitivity kernels from standard perturbation analysis for forward modeling. Using this method, we demonstrate that offset fields may be mistaken for weak and centered magnetic fields, resulting in underestimating magnetic field strength in stellar cores. We emphasize the need to characterize $\ell =2$ mixed-mode frequencies, (along with the currently characterized $\ell =1$ mixed modes), to unveil the higher-order components of the geometry of buried magnetic fields, and better constrain angular momentum transport inside stars.

Submitted to Astronomy and Astrophysics, 17 pages, 11 figures and 1 table

References in corpus (62)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Dynamo action by differential rotation in a stably stratified stellar interior
• Magnetic fields of non-degenerate stars
• Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure
• GYRE: An open-source stellar oscillation code based on a new Magnus Multiple Shooting Scheme
• Fast core rotation in red-giant stars revealed by gravity-dominated mixed modes
• Seismic evidence for a rapidly rotating core in a lower-giant-branch star observed with Kepler
• Slowing the Spins of Stellar Cores
• Seismic constraints on the radial dependence of the internal rotation profiles of six Kepler subgiants and young red giants
• Seismic diagnostics for transport of angular momentum in stars 1. Rotational splittings from the PMS to the RGB
• Characterization of the power excess of solar-like oscillations in red giants with Kepler
• Seismic evidence for a weak radial differential rotation in intermediate-mass core helium burning stars
• Core rotation braking on the red giant branch for various mass ranges
• On non-axisymmetric magnetic equilibria in stars
• Transport and mixing in the radiation zones of rotating stars II. Axisymmetric magnetic field
• Seismic diagnostics for transport of angular momentum in stars 2. Interpreting observed rotational splittings of slowly-rotating red giant stars
• Understanding angular momentum transport in red giants: the case of KIC 7341231
• Internal rotation of the red-giant star KIC 4448777 by means of asteroseismic inversion
• An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova
• Impact of rotation and disc lifetime on pre-main sequence lithium depletion of solar-type stars
• 30 to 100-kG magnetic fields in the cores of red giant stars
• Deep Learning Classification in Asteroseismology
• Seismic evidence for near solid-body rotation in two Kepler subgiants and implications for angular momentum transport
• Zeeman tomography of magnetic white dwarfs IV. The complex field structure of the polars EF Eri, BL Hyi, and CP Tuc
• Strong magnetic fields detected in the cores of 11 red giant stars using gravity-mode period spacings
• Magnetic signatures on mixed-mode frequencies. I. An axisymmetric fossil field inside the core of red giants
• WD1953-011 - a magnetic white dwarf with peculiar field structure
• Period spacings of gravity modes in rapidly rotating magnetic stars I. Axisymmetric fossil field with poloidal and toroidal components
• Internal rotation of 13 low-mass low-luminosity red giants in the Kepler field
• Near-degeneracy effects on the frequencies of rotationally-split mixed modes in red giants
• Rotation in stellar interiors: General formulation and an asteroseismic-calibrated transport by the Tayler instability
• Spectrophotometric analysis of magnetic white dwarf I: Hydrogen-rich compositions
• A Search for Red Giant Solar-like Oscillations in All Kepler Data
• Zeeman tomography of magnetic white dwarfs III. The 70-80 Megagauss magnetic field of PG 1015+014
• Detecting Solar-like Oscillations in Red Giants with Deep Learning
• Spin-down by dynamo action in simulated radiative stellar layers
• Zeeman tomography of magnetic white dwarfs II. The quadrupole-dominated magnetic field of HE 1045-0908
• Effect of a strong magnetic field on gravity-mode period spacings in red giant stars
• Asteroseismic measurement of core and envelope rotation rates for 2006 red giant branch stars
• Asteroseismic Signatures of Core Magnetism and Rotation in Hundreds of Low-Luminosity Red Giants
• Magnetic Helicity and the Relaxation of Fossil Fields
• Monitoring and modelling of white dwarfs with extremely weak magnetic fields
• Topology and obliquity of core magnetic fields in shaping seismic properties of slowly rotating evolved stars
• A DZ white dwarf with a 30 MG magnetic field
• Angular momentum transport by magnetic fields in main sequence stars with Gamma Doradus pulsators
• Asymmetries of frequency splittings of dipolar mixed modes: a window on the topology of deep magnetic fields
• Magnetic signatures on mixed-mode frequencies. II. Period spacings as a probe of the internal magnetism of red giants
• beta Cas: the first delta Scuti star with a dynamo magnetic field
• Core magnetic field imprint in the non-radial oscillations of red giant stars
• Automated approach to measure stellar inclinations: validation through large-scale measurements on the red giant branch
• The complex magnetic field topology of the cool Ap star 49 Cam
• Asteroseismic sensitivity to internal rotation along the red-giant branch
• Spectrophotometric analysis of magnetic white dwarf II: Helium-rich compositions
• Sensitivity kernels for inferring Lorentz stresses from normal-mode frequency splittings in the Sun
• Magnetic field topology, chemical spot distributions and photometric variability of the Ap star phi Draconis
• Analysis of Solar-like X-Class Flare on Wolf 359 Observed Simultaneously with TESS and XMM-Newton
• GYRE: A New Open-Source Stellar Oscillation Code
• Asteroseismogyrometry of low-mass red giants I. The SOLA inversion method

Cited by in corpus (7)

• Oscillations of red giant stars with magnetic damping in the core. I. Dissipation of mode energy in dipole-like magnetic fields
• Pushing the boundaries of asteroseismic individual frequency modelling: unveiling two evolved very-low metallicity red giants
• Interior rotation modelling of the $\beta$ Cep pulsator HD 192575 including multiplet asymmetries
• Exploring the probing power of gamma-Dor's inertial dip for core magnetism: case of a toroidal field
• Near-critical magnetic fields in Kepler red giants
• Magneto-Archeology of White Dwarfs. Revisiting the fossil field scenario with observational constraints during the red giant branch
• Near-degeneracy effects in Quadrupolar Mixed Modes. From an Asymptotic Description to Data Fitting