Slow pressure modes in thin accretion discs

Tarun Deep Saini; Mamta Gulati; S. Sridhar

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arXiv · 0901.4229

Slow pressure modes in thin accretion discs

Tarun Deep Saini·Mamta Gulati·S. Sridhar

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Abstract

Thin accretion discs around massive compact objects can support slow pressure modes of oscillations in the linear regime that have azimuthal wavenumber $m=1$. We consider finite, flat discs composed of barotropic fluid for various surface density profiles and demonstrate--through WKB analysis and numerical solution of the eigenvalue problem--that these modes are stable and have spatial scales comparable to the size of the disc. We show that the eigenvalue equation can be mapped to a Schrödinger-like equation. Analysis of this equation shows that all eigenmodes have discrete spectra. We find that all the models we have considered support negative frequency eigenmodes; however, the positive eigenfrequency modes are only present in power law discs, albeit for physically uninteresting values of the power law index $β$ and barotropic index $γ$.

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Tarun Deep Saini, Mamta Gulati, S. Sridhar. 2009-11-23. Slow pressure modes in thin accretion discs. https://arxiv.org/abs/0901.4229

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