PREPARING FOR AN EXPLOSION: HYDRODYNAMIC INSTABILITIES AND TURBULENCE IN PRESUPERNOVAE

Both observations and numerical simulations are discordant with predictions of conventional stellar evolution codes for the latest stages of a massive star's life before core collapse. The most dramatic example of this disconnect is in the eruptive mass loss occurring in the decade preceding Ty...

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Bibliographic Details
Published in:The Astrophysical journal 2014-04, Vol.785 (2), p.1-12
Main Authors: Smith, Nathan, Arnett, W David
Format: Article
Language:English
Subjects:
ABUNDANCE
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Combustion
Computational fluid dynamics
COMPUTERIZED SIMULATION
CONVECTION
ERUPTION
FLUCTUATIONS
Fluid flow
FORECASTING
INSTABILITY
Mathematical models
METEORITES
METEOROIDS
MIXING
MODIFICATIONS
NUCLEAR REACTIONS
NUCLEOSYNTHESIS
Stability
STAR EVOLUTION
STELLAR WINDS
SUPERNOVA REMNANTS
SUPERNOVAE
TURBULENCE
Turbulent flow
VELOCITY
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Summary:Both observations and numerical simulations are discordant with predictions of conventional stellar evolution codes for the latest stages of a massive star's life before core collapse. The most dramatic example of this disconnect is in the eruptive mass loss occurring in the decade preceding Type IIn supernovae. We outline the key empirical evidence that indicates severe pre-supernova instability in massive stars, and we suggest that the chief reason that these outbursts are absent in stellar evolution models may lie in the treatment of turbulent convection in these codes. The mixing length theory that is used ignores (1) finite amplitude fluctuations in velocity and temperature and (2) their nonlinear interaction with nuclear burning. Including these fluctuations is likely to give rise to hydrodynamic instabilities in the latest burning sequences, which prompts us to discuss a number of far-reaching implications for the fates of massive stars. In particular, we explore connections to enhanced pre-supernova mass loss, unsteady nuclear burning and consequent eruptions, swelling of the stellar radius that may trigger violent interactions with a companion star, and potential modifications to the core structure that could dramatically alter calculations of the core-collapse explosion mechanism itself. These modifications may also impact detailed nucleosynthesis and measured isotopic anomalies in meteorites, as well as the interpretation of young core-collapse supernova remnants. Understanding these critical instabilities in the final stages of evolution may make possible the development of an early warning system for impending core collapse, if we can identify their asteroseismological or eruptive signatures.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/785/2/82