Oscillations in radiation-driven outflows

• Published in: Monthly notices of the Royal Astronomical Society Vol. 299; no. 1; pp. 139 - 149
• Main Authors: Miller, Guy S., Grossman, Scott A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-09-1998
• Subjects: hydrodynamics; stars: neutron; stars: oscillations; X-rays: bursts
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1046/j.1365-8711.1998.01759.x

In this paper we investigate the dynamical behaviour of radiation-driven winds, specifically winds that arise when Compton scattering transfers momentum from the radiation field to the gas flow. Such winds occur during strong X-ray bursts from slowly accreting neutron stars, and also may be driven from the inner regions of a black hole or neutron star accretion disc when the mass transfer rate is very high. By linearizing the radiation hydrodynamic equations around steady spherical outflow, we evaluate the time-dependent response of these winds to perturbations introduced at their inner boundaries. We find that although radiation-driven winds are generally stable, they act as mechanical filters that should produce quasi-periodic oscillations or peaked noise in their radiation output when perturbations force them stochastically. This behaviour may underlie the photospheric oscillations observed in some strong Type I X-ray bursts.