Schedule Mar 23, 2007
Thermally Stable Nuclear Burning on Accreting White Dwarfs
Ken Shen (UCSB)

Authors: Ken Shen and Lars Bildsten

One of the challenges to increasing the mass of a white dwarf throughaccretion is the tendency for the accumulating hydrogen to ignite unstablyand potentially trigger mass loss. It has been known for many years thatthere is a narrow range of accretion rates for which the hydrogen can burnstably, allowing for the white dwarf mass to increase as a pure heliumlayer accumulates. We first review the physics of stable burning,providing a clear explanation for why radiation pressure stabilizationleads to a narrow range of accretion rates for stable burning near theEddington limit, confirming the recent work of Nomoto and collaborators.We also explore the possibility of stabilization due to a high luminosityfrom beneath the burning layer. We then examine the impact of thebeta-decay-limited ``hot'' CNO cycle on the stability of burning. Thoughthis plays a significant role for accreting neutron stars, we find thatfor accreting white dwarfs, it can only increase the range ofstably-burning accretion rates for metallicities below 0.01 solarmetallicity.

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