Internal heating and thermal emission from old neutron stars |
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| Authors: | Andreas Reisenegger Rodrigo Fernández Paula Jofré |
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| Institution: | (1) Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago, 22, Chile;(2) Department of Astronomy & Astrophysics, University of Toronto, Toronto, ON, M5S 3H8, Canada;(3) Present address: Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching bei München, Germany |
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| Abstract: | The equilibrium composition of neutron star matter is achieved through weak interactions (direct and inverse beta decays),
which proceed on relatively long time scales. If the density of a matter element is perturbed, it will relax to the new chemical
equilibrium through non-equilibrium reactions, which produce entropy that is partly released through neutrino emission, while
a similar fraction heats the matter and is eventually radiated as thermal photons. We examined two possible mechanisms causing
such density perturbations: (1) the reduction in centrifugal force caused by spin-down (particularly in millisecond pulsars),
leading to rotochemical heating, and (2) a hypothetical time-variation of the gravitational constant, as predicted by some theories of gravity and current
cosmological models, leading to gravitochemical heating. If only slow weak interactions are allowed in the neutron star (modified Urca reactions, with or without Cooper pairing),
rotochemical heating can account for the observed ultraviolet emission from the closest millisecond pulsar, PSR J0437-4715,
which also provides a constraint on |dG/dt| of the same order as the best available in the literature.
This work made use of NASA’s Astrophysics Data System Service, and received financial support from FONDECYT through regular
grants 1020840 and 1060644. |
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| Keywords: | Stars: neutron Dense matter Relativity Stars: rotation Pulsars: general Pulsars: individual (PSR B0950+08 PSR J0108-1431 PSR J0437-4715) |
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