The nature of the radiative hydrodynamic instabilities in radiatively supported Thomson atmospheres

Nir J. Shaviv*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

Atmospheres having a significant radiative support are shown to be intrinsically unstable at luminosities above a critical fraction Γcrit ≈ 0.5-0.85 of the Eddington limit, with the exact value depending on the boundary conditions. Two different types of absolute radiation-hydrodynamic instabilities of acoustic waves are found to take place even in the electron scattering-dominated limit. Both instabilities grow over dynamical timescales and both operate on nonradial modes. One is stationary and arises only after the effects of the boundary conditions are taken into account, while the second is a propagating wave and is insensitive to the boundary conditions. Although a significant wind can be generated by these instabilities even below the classical Eddington luminosity limit, quasi-stable configurations can exist beyond the Eddington limit due to the generally reduced effective opacity. The study is done using a rigorous numerical linear analysis of a gray plane-parallel atmosphere under the Eddington approximation. We also present more simplified analytical explanations.

Original languageAmerican English
Pages (from-to)1093-1110
Number of pages18
JournalAstrophysical Journal
Volume549
Issue number2 PART 1
DOIs
StatePublished - 10 Mar 2001
Externally publishedYes

Keywords

  • Hydrodynamics
  • Instabilities
  • Radiative transfer
  • Stars: atmospheres
  • Stars: oscillations
  • Stars: variables: other

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