Volume 480, Number 2, March III 2008
|Page(s)||459 - 464|
|Section||Stellar structure and evolution|
|Published online||09 January 2008|
Models of crustal heating in accreting neutron stars*
N. Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, 00-716 Warszawa, Poland e-mail: [haensel;jlz]@camk.edu.pl
Accepted: 8 November 2007
Aims.We calculate heating associated with non-equilibrium nuclear reactions in accreting neutron-star crusts, taking into account the suppression of neutrino losses demonstrated recently by Gupta et al. We consider two initial compositions of the nuclear-burning ashes, Ai = 56 and Ai = 106. We study the dependence of the integrated crustal heating on uncertainties plaguing pycnonuclear reaction models.
Methods.We use one-component plasma approximation, with compressible liquid-drop model of Mackie and Baym to describe nuclei. We follow the evolution of a crust shell from 108 g cm-3 to 1013.6 g cm-3.
Results.The integrated heating in the outer crust agrees nicely with results of self-consistent multicomponent plasma simulations: earlier results fall between our curves obtained for Ai = 56 and Ai = 106. The total crustal heat per one accreted nucleon ranges between 1.5 MeV/nucleon to 1.9 MeV/nucleon for Ai = 106 and Ai = 56, respectively. The value of Qtot weakly depends on the presence of pycnonuclear reactions at 1012-1013 g cm-3. The remarkable insensitivity of Qtot to the distribution of nuclear processes in accreted crust is explained.
Key words: dense matter / equation of state / stars: neutron / stars: general / X-rays: bursts / X-ray: binaries
© ESO, 2008
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