2003/12/22 by P. Chang, Philip Chang, Lars Bildsten +1
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics #Atomic and Subatomic Physics Research #Diffusion #Dipole #High-pressure geophysics and materials #Hydrogen #Limiting #Magnetic field #Magnitude (astronomy) #Neutron #Neutron star #Nuclear physics #Physics #Proton #Pulsar #Pulsars and Gravitational Waves Research #Stars #Thermodynamics #astro-ph
paper · pdf · doi:10.1086/382271
published as Astrophys.J.605:830-839,2004 · 10 pages, 8 figures, to appear in ApJ
arxiv created 2003/12/22 · openalex publication_date 2004/04/09 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/08
We extend our initial study of diffusive nuclear burning (DNB) for neutron stars (NSs) with hydrogen (H) atmospheres and an underlying layer of proton-capturing nuclei. Our initial study showed that DNB can alter the photospheric abundance of hydrogen on surprisingly short timescales (10 2 -10 4 yr). Significant composition evolution impacts the radiated thermal spectrum from the NS as well as its overall cooling rate. In this paper, we consider the case when the rate-limiting step for the H consumption is diffusion to the burning layer rather than the local nuclear timescale. This is relevant for NSs with surface temperatures in excess of 10 6 K, such as young (<10 5 yr) radio pulsars and accreting NSs in quiescence. When downward diffusion is the limiting rate in DNB, the rate of H consumption is suppressed by 1-2 orders of magnitude compared to a DNB estimate that assumes diffusive equilibrium. In order to apply our ongoing study to young neutron stars, we also include the important effects of strong magnetic fields ( B ~ 10 12 G). In this initial study of magnetic modifications to DNB, we find that the H-burning time is lengthened by 2-3 orders of magnitude for a 10 12 G field. However, even for NSs with dipole field strengths of 10 12 G, we find that all of the H can be burned before the pulsar reaches an age of ~10 5 yr, thus potentially revealing the underlying proton-capturing elements. Finally, we conclude by providing an overview of what can be learned about fallback and pulsar winds from measuring the surface composition of a young NS.