Rodrigo Negreiros, Stefan Schramm, Fridolin Weber
Driven by the loss of energy, isolated rotating neutron stars (pulsars) are
gradually slowing down to lower frequencies, which monotonically increases the
tremendous compression of the matter inside of them. This increase in
compression changes both the global properties of rotating neutron stars as
well as their hadronic core compositions. Both effects may register themselves
observationally in the thermal evolution of such stars, as demonstrated in this
Letter. The rotation-driven particle process which we consider is the direct
Urca (DU) process, which is known to become operative in neutron stars if the
number of protons in the stellar core exceeds a critical limit of around 11% to
15%. We find that neutron stars spinning down from moderately high rotation
rates of a few hundred Hertz may be creating just the right conditions where
the DU process becomes operative, leading to an observable effect (enhanced
cooling) in the temperature evolution of such neutron stars. We also find that
the rotation-driven DU process can comfortably explain the temperatures
observed for the neutron star in Cas A provided the mass of this neutron star
is assumed to be around 1.5 -- 1.9 \msun. Finally, a preliminary estimate of
the temperature of the recently discovered massive neutron star PSR J1614-2230,
which rotates at 317 Hz, indicates that the rotation-driven DU process may have
cooled this neutron star to remarkably low temperatures of $\lsim 10^6$ K.
View original:
http://arxiv.org/abs/1103.3870
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