J/A+A/645/A102 Crust structure of neutron stars (Potekhin+, 2021)
Crust structure and thermal evolution of neutron stars in soft X-ray transients.
Potekhin A.Y., Chabrier G.
<Astron. Astrophys. 645, A102 (2021)>
=2021A&A...645A.102P 2021A&A...645A.102P
ADC_Keywords: Models
Keywords: stars: neutron - dense matter - X-rays: binaries -
X-rays: individuals: MXB 1659-29
Abstract:
The thermal evolution of neutron stars in soft X-ray transients (SXTs)
is sensitive to the equation of state, nucleon superfluidity, and the
composition and structure of the crust. Carrying out comparisons of
the observations of their crust cooling with simulations offers a
powerful tool for verifying theoretical models of dense matter.
We study the effect of physics input on the thermal evolution of
neutron stars in SXTs. In particular, we consider different modern
models of the sources of deep crustal heating during accretion
episodes and the effects brought on by impurities embedded in the
crust during its formation.
We simulated the thermal structure and evolution of episodically
accreting neutron stars under different assumptions regarding the
crust composition and on the distribution of heat sources and
impurities. For the non-accreted crust, we considered the nuclear
charge fluctuations that arise at crust formation. For the accreted
crust, we compared different theoretical models of composition and
internal heating. We also compared the results of numerical
simulations to observations of the crust cooling in SXT MXB 1659-29.
The non-accreted part of the inner crust of a neutron star can have a
layered structure, with almost pure crystalline layers interchanged
with layers composed of mixtures of different nuclei. The latter
layers have relatively low thermal conductivities, which has an effect
on the thermal evolution of the transients. The impurity distribution
in the crust strongly depends on models of the dense matter and the
crust formation scenario. The shallow heating that is needed to reach
an agreement between the theory and the observations depends on
characteristics of the crust and envelope.
Description:
The tables present average parameters of a Wigner-Seitz cell in an
inner crust of a neutron star, considering nuclear mixtures that arise
due to the nuclear statistical equilibrium conditions at the original
crust formation. The four tables represent results of computations
performed according to the Brussels-Montreal equation-of-state (EoS)
models BSk22, BSk24, BSk25, and BSk26. For different mean number
densities of baryons n_bar, each table gives an average number of
protons in a Wigner-Seitz cell Z_cell, an average number of protons in
a nuclear cluster at the center of a Wigner-Seitz cell Z_clust, an
average number of nucleons (protons and neutrons) in a Wigner-Seitz
cell A_cell, an average number of nucleons in a nuclear cluster at the
center of a Wigner-Seitz cell A_clust, and the impurity parameter (the
mean-square deviation of Z_clust from its average value) Q_imp.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
qimp22.dat 67 62 Inner crust properties for model BSk22
qimp24.dat 67 62 Inner crust properties for model BSk24
qimp25.dat 67 97 Inner crust properties for model BSk25
qimp26.dat 67 62 Inner crust properties for model BSk26
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Byte-by-byte Description of file: qimp22.dat qimp24.dat qimp25.dat qimp26.dat
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Bytes Format Units Label Explanations
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1- 11 E11.3 fm-3 nbar Mean number density of baryons (n_bar)
12- 23 E12.3 --- Zcell Mean number of protons per Wigner-Seitz cell
(Z_cell)
24- 33 E10.3 --- Zclust Mean number of bound protons in a nucleus
(Z_clust)
34- 45 E12.3 --- Acell Mean number of nucleons per Wigner-Seitz cell
(A_cell)
46- 55 E10.3 --- Aclust Mean number of bound nucleons in a nucleus
(A_clust)
56- 67 E12.3 --- Qimp Impurity parameter (Q_imp)
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Acknowledgements:
Alexander Potekhin, palex(at)astro.ioffe.ru
(End) Patricia Vannier [CDS] 25-Nov-2020