A Diagnostic for Localizing Red Giant Differential Rotation

Abstract

We present a simple diagnostic that can be used to constrain the location of the differential rotation in red giants with measured mixed mode rotational splittings. Specifically, in red giants with radii $\sim 4R_{\odot }$, the splittings of p-dominated modes (sound wave dominated) relative to those of g-dominated modes (internal gravity wave dominated) are sensitive to how much of the differential rotation resides in the outer convection zone versus the radiative interior of the red giant. An independently measured surface rotation rate significantly aids breaking degeneracies in interpreting the measured splittings. We apply our results to existing observations of red giants, particularly those of Kepler-56, and find that most of the differential rotation resides in the radiative region rather than in the convection zone. This conclusion is consistent with results in the literature from rotational inversions, but our results are insensitive to some of the uncertainties in the inversion process and can be readily applied to large samples of red giants with even a modest number of measured rotational splittings. We argue that differential rotation in the radiative interior strongly suggests that angular momentum transport in red giants is dominated by local fluid instabilities rather than large-scale magnetic stresses.

6 pages, 4 figures, submitted to MNRAS Letters

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Cited by in corpus (21)

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• Asteroseismology of evolved stars to constrain the internal transport of angular momentum II. Test of a revised prescription for transport by the Tayler instability
• Internal rotation of 13 low-mass low-luminosity red giants in the Kepler field
• Rotation in stellar interiors: General formulation and an asteroseismic-calibrated transport by the Tayler instability
• Asteroseismic Fingerprints of Stellar Mergers
• The rotational shear layer inside the early red-giant star KIC 4448777
• Testing Angular Momentum Transport and Wind Loss in Intermediate Mass Core Helium Burning Stars
• Asteroseismology of evolved stars to constrain the internal transport of angular momentum. IV. Internal rotation of Kepler 56 from an MCMC analysis of the rotational splittings
• Asteroseismology of evolved stars to constrain the internal transport of angular momentum. V. Efficiency of the transport on the red giant branch and in the red clump
• Rotation and Magnetism of Massive Stellar Cores
• Asteroseismic sensitivity to internal rotation along the red-giant branch
• Mode Mixing and Rotational Splittings: I. Near-Degeneracy Effects Revisited
• Convective Differential Rotation in Stars and Planets I: Theory
• Improved asteroseismic inversions for red-giant surface rotation rates
• Differential Rotation in Convective Envelopes: Constraints from Eclipsing Binaries
• Magnetic Webs in Stellar Radiative Zones
• Tidal disruption event associated with the quasi-periodic eruptions from GSN 069: Possible disruption of a common envelope
• Convective Differential Rotation in Stars and Planets II: Observational and Numerical Tests
• The robustness of inferred envelope and core rotation rates of red-giant stars from asteroseismology
• The efficiency of mixed modes for angular momentum transport
• Impact of near-degeneracy effects on linear rotational inversions for red-giant stars