|
Close Details
|
|
2012 - 11th Annual NC State Summer Undergraduate Research Symposium
|
|
Session Time :
8/1/12 1:30 PM - 8/1/12 2:45 PM
|
|
Content Area : NSF Physics REU
|
Lead Student Presenters : Anna Susan Carr
|
Abstract Title : Breathing Mode Instability in Hoyle-Lyttleton Accretion
|
Abstract :
Gravitational accretion serves as a ubiquitous source of power for many celestial objects, yet its fundamental properties remain poorly understood. Proposed in 1939, the Hoyle-Lyttleton model of accretion describes mathematically the behavior of a uniform gas cloud collecting onto a compact star. While this model has been found to predict generally accurate data, it is limited to steady, axisymmetric flow and fails to address the temporal variability seen in many accreting x-ray sources. Recent studies of high-resolution simulations of HL accretion demonstrated instability in the mass accretion rate creating breathing mode oscillations of unclear origin. We conducted an in-depth investigation of accretion breathing modes using 2D simulations to characterize their nature as a function of varying conditions and were able to confirm their existence. The instabilities were only observed when the accretor radius was less than Rs= 0.02Ra. Additionally, We found that when the adiabatic index deviated from γ = 5/3, the properties of the instabilities changed. As the adiabatic index became smaller, the period of the oscillations decreased while their regularity increased.
|
Mentor and/or Co-Author : John M. Blondin
|