The role of the magnetorotational instability in massive stars

J. Craig Wheeler, Daniel Kagan, Emmanouil Chatzopoulos

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

The magnetorotational instability (MRI) is key to physics in accretion disks and is widely considered to play some role in massive star core collapse. Models of rotating massive stars naturally develop very strong shear at composition boundaries, a necessary condition for MRI instability, and the MRI is subject to triply diffusive destabilizing effects in radiative regions. We have used the MESA stellar evolution code to compute magnetic effects due to the Spruit-Tayler (ST) mechanism and the MRI, separately and together, in a sample of massive star models. We find that the MRI can be active in the later stages of massive star evolution, leading to mixing effects that are not captured in models that neglect the MRI. The MRI and related magnetorotational effects can move models of given zero-age main sequence mass across "boundaries" from degenerate CO cores to degenerate O/Ne/Mg cores and from degenerate O/Ne/Mg cores to iron cores, thus affecting the final evolution and the physics of core collapse. The MRI acting alone can slow the rotation of the inner core in general agreement with the observed "initial" rotation rates of pulsars. The MRI analysis suggests that localized fields ∼1012 G may exist at the boundary of the iron core. With both the ST and MRI mechanisms active in the 20 M model, we find that the helium shell mixes entirely out into the envelope. Enhanced mixing could yield a population of yellow or even blue supergiant supernova progenitors that would not be standard SN IIP.

Original languageEnglish
Article number85
JournalAstrophysical Journal
Volume799
Issue number1
DOIs
StatePublished - 20 Jan 2015
Externally publishedYes

Keywords

  • Instabilities
  • Magnetohydrodynamics (MHD)
  • Stars: Magnetic fields
  • Stars: Neutron
  • Stars: Rotation
  • Supernovae: General

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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