Speaker
Description
The mechanism of angular momentum transport in a neutron star boundary layer (BL) is still a major open problem in accretion disc theory. As well as the cooling curve after a type 1 thermonuclear burst, which requires some unexplained shallow heating source to explain its relaxation time. In this work, we show that acoustic waves generated in the BL due to the supersonic shear are both efficient at transporting angular momentum in a general relativistic regime and are a plausible candidate for shallow heating. We have performed 2D General Relativistic Hydrodynamic Simulations in the equatorial plane assuming a Schwarzschild metric. We have tested the influence of two different equations of state, the stellar compactness, and the Mach number. We found that the BL tends to thicken to 10-40% of the stellar radius. The heating of the BL is spread out into the disc up to twice the stellar radius. Furthermore, the shocks also transport heat into the star. These shocks deposit between 3-20 MeV / accreted nucleon of heat, which also matches the required shallow heating sources. This result shows that the sonic instability is a plausible candidate to explain shallow heating.
| Talk category | NOVA Network 3 |
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