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S. Starrfield (ASU), J. W. Truran (Chicago), J. MacDonald (Delaware), W. M. Sparks (LANL)
We have begun a new series of calculations of accretion onto 10 km, 1.4M\odot neutron stars. We are using our 1-D, implicit, Lagrangian hydro-code, NOVA (Starrfield et al. MNRAS, 296, 502, 1998; ApJS, 127, 485, 2000), which includes both a large nuclear reaction network and elemental diffusion (Iben and MacDonald ApJ, 296, 540). In our exploratory calculations, we have varied both the initial neutron star luminosity and mass accretion rate choosing similar values to those used by other investigators to successfully simulate X-ray bursts. We have found, however, for some previously successful sets of initial conditions, that accretion in the presence of diffusion causes the hydrogen to float to the surface. A thick layer of nuclear processed accreted material then grows under the proton rich surface layers and no X-ray burst occurs. Our simulations done with identical initial conditions but without the inclusion of diffusion do result in X-ray bursts.
We gratefully acknowledge partial support from grants to our institutions from NASA, NSF, and the DOE.
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The author(s) of this abstract have provided an email address for comments about the abstract: starrfield@asu.edu