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Title: THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS

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 ∼10{sup 12} G may exist at the boundary ofmore » the iron core. With both the ST and MRI mechanisms active in the 20 M {sub ☉} 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.« less

Authors:
 [1];  [2];  [3]
  1. Department of Astronomy, University of Texas at Austin, Austin, TX (United States)
  2. Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904 (Israel)
  3. Department of Astronomy and Astrophysics and FLASH Center for Computational Science, University of Chicago, Chicago, IL 60637 (United States)
Publication Date:
OSTI Identifier:
22364445
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 799; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; CARBON MONOXIDE; HELIUM; IRON; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MASS; NEUTRONS; ROTATION; SHEAR; STAR EVOLUTION; STAR MODELS; SUPERNOVAE

Citation Formats

Wheeler, J. Craig, Kagan, Daniel, and Chatzopoulos, Emmanouil, E-mail: wheel@astro.as.utexas.edu. THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS. United States: N. p., 2015. Web. doi:10.1088/0004-637X/799/1/85.
Wheeler, J. Craig, Kagan, Daniel, & Chatzopoulos, Emmanouil, E-mail: wheel@astro.as.utexas.edu. THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS. United States. doi:10.1088/0004-637X/799/1/85.
Wheeler, J. Craig, Kagan, Daniel, and Chatzopoulos, Emmanouil, E-mail: wheel@astro.as.utexas.edu. Tue . "THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS". United States. doi:10.1088/0004-637X/799/1/85.
@article{osti_22364445,
title = {THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS},
author = {Wheeler, J. Craig and Kagan, Daniel and Chatzopoulos, Emmanouil, E-mail: wheel@astro.as.utexas.edu},
abstractNote = {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 ∼10{sup 12} G may exist at the boundary of the iron core. With both the ST and MRI mechanisms active in the 20 M {sub ☉} 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.},
doi = {10.1088/0004-637X/799/1/85},
journal = {Astrophysical Journal},
number = 1,
volume = 799,
place = {United States},
year = {Tue Jan 20 00:00:00 EST 2015},
month = {Tue Jan 20 00:00:00 EST 2015}
}