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Slowing the Spins of Stellar Cores

Fuller, Jim and Piro, Anthony L. and Jermyn, Adam S. (2019) Slowing the Spins of Stellar Cores. Monthly Notices of the Royal Astronomical Society, 485 (3). pp. 3661-3680. ISSN 0035-8711. doi:10.1093/mnras/stz514.

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The angular momentum (AM) evolution of stellar interiors, along with the resulting rotation rates of stellar remnants, remains poorly understood. Asteroseismic measurements of red giant stars reveal that their cores rotate much faster than their surfaces, but much slower than theoretically predicted, indicating an unidentified source of AM transport operates in their radiative cores. Motivated by this, we investigate the magnetic Tayler instability and argue that it saturates when turbulent dissipation of the perturbed magnetic field energy is equal to magnetic energy generation via winding. This leads to larger magnetic field amplitudes, more efficient AM transport, and smaller shears than predicted by the classic Tayler–Spruit dynamo. We provide prescriptions for the effective AM diffusivity and incorporate them into numerical stellar models, finding they largely reproduce (1) the nearly rigid rotation of the Sun and main sequence stars, (2) the core rotation rates of low-mass red giants during hydrogen shell and helium burning, and (3) the rotation rates of white dwarfs. We discuss implications for stellar rotational evolution, internal rotation profiles, rotational mixing, and the spins of compact objects.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Fuller, Jim0000-0002-4544-0750
Piro, Anthony L.0000-0001-6806-0673
Jermyn, Adam S.0000-0001-5048-9973
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 February 17. Received 2019 February 17; in original form 2018 June 17. We thank the referee for constructive and much-deserved critiques. We thank Peter Goldreich, Marc Pinsonneault, Matteo Cantiello, and Daniel Lecoanet for useful discussions. This research is funded in part by an Innovator Grant from The Rose Hills Foundation, the Gordon and Betty Moore Foundation through Grant GBMF7392, and by the National Science Foundation under Grant No. NSF PHY-1748958.
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
Rose Hills FoundationUNSPECIFIED
Gordon and Betty Moore FoundationGBMF7392
Subject Keywords:astroseismology, instabilities, MHD, stars: evolution, stars: interiors, stars: rotation
Issue or Number:3
Record Number:CaltechAUTHORS:20190425-152212984
Persistent URL:
Official Citation:Jim Fuller, Anthony L Piro, Adam S Jermyn, Slowing the spins of stellar cores, Monthly Notices of the Royal Astronomical Society, Volume 485, Issue 3, May 2019, Pages 3661–3680,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94990
Deposited By: George Porter
Deposited On:25 Apr 2019 23:15
Last Modified:16 Nov 2021 17:09

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