1,128 research outputs found

### Electron conduction along quantizing magnetic fields in neutron star crusts. I. Theory

Transport properties of degenerate relativistic electrons along quantizing
magnetic fields in neutron star crusts are considered. A kinetic equation is
derived for the spin polarization density matrix of electrons. Its solution
does not depend on the choice of basic electron wave functions unlike previous
solutions of the traditional kinetic equation for the distribution function.
The density matrix formalism shows that one can always reach high accuracy with
the traditional method by a proper choice of the basic functions. Electron
Coulomb scattering on ions is considered in liquid matter, and on
high-temperature phonons or on charged impurities in solid matter. In the solid
regime, the Debye -- Waller reduction of phonon scattering can strongly enhance
the longitudinal thermal or electric conductivity. An efficient numerical
method is proposed for calculating the transport properties of electron gas at
any magnetic field of practical interest.Comment: 12 pages, A&A-LaTeX (l-aa.sty included), 2 PostScript figures. A
misprint in Eq. (B3) correcte

### Atmospheres and radiating surfaces of neutron stars

The early 21st century witnesses a dramatic rise in the study of thermal
radiation of neutron stars. Modern space telescopes have provided a wealth of
valuable information which, when properly interpreted, can elucidate the
physics of superdense matter in the interior of these stars. This
interpretation is necessarily based on the theory of formation of neutron star
thermal spectra, which, in turn, is based on plasma physics and on the
understanding of radiative processes in stellar photospheres. In this paper,
the current status of the theory is reviewed with particular emphasis on
neutron stars with strong magnetic fields. In addition to the conventional deep
(semi-infinite) atmospheres, radiative condensed surfaces of neutron stars and
"thin" (finite) atmospheres are considered.Comment: 43 pages, 13 figures, 1 table. In v.3, there are more than 50 minor
corrections (typos, wording, style) and one important typo fix (the sign in
Eq.(61)). In v.4, beside a few minor improvements, ionization equilibrium
equation (58) is corrected. In v.5, a typo in Eq.(12) is fixe

### Hydrogen atom in a magnetic field: The quadrupole moment

The quadrupole moment of a hydrogen atom in a magnetic field for field
strengths from 0 to 4.414e13 G is calculated by two different methods. The
first method is variational, and based on a single trial function. The second
method deals with a solution of the Schroedinger equation in the form of a
linear combination of Landau orbitals.Comment: 4 pages, 1 figure, 1 table; RevTeX. Final (proofs-stage) version of
the text; corrected numbers in Table 1 and in Eq.(15

### Comment on "On the ionization equilibrium of hot hydrogen plasma and thermodynamic consistency of formulating finite partition functions"

Zaghloul [Phys. Plasmas 17, 062701 (2010); arXiv:1010.1161v1] reconsiders the
occupation probability formalism in plasma thermodynamics and claims
inconsistencies in previous models. I show that the origin of this incorrect
claim is an omission of the configurational factor from the partition function.
This arXiv version is supplemented with two appendices, where I add remarks and
comments on two more recent publications of the same author on the same
subject: on his response to this Comment [Phys. Plasmas 17, 124705 (2010)] and
on his criticism towards the Hummer and Mihalas's (1988) formalism [Phys.
Plasmas 17, 122903 (2010); arXiv:1010.1102v1].Comment: 4 pages: 2 pages of the journal publication + 2 pages of the
electronic supplemen

### Dense astrophysical plasmas

We briefly examine the properties of dense plasmas characteristic of the
atmospheres of neutron stars and of the interior of massive white dwarfs. These
astrophysical bodies are natural laboratories to study respectively the problem
of pressure ionization of hydrogen in a strong magnetic field and the
crystallization of the quantum one-component-plasma at finite temperature.Comment: 8 pages, 3 figures, LaTeX using iopart.cls and iopart12.clo
(included). In the special issue "Liquid State Theory: from White Dwarfs to
Colloids" (International Conf. in the honor of Prof. J.-P. Hansen's 60th
birthday, Les Houches, April 1-5, 2002

### Evolution of Young Neutron Star Envelopes

We extend our initial study of diffusive nuclear burning (DNB) for neutron
stars (NSs) with Hydrogen 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^{2-4}\yrs).
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 $10^6 {\rm K}$, 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 ($B \sim 10^{12} {\rm G}$). 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 $10^{12} {\rm G}$ 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 $\sim 10^5 \
{\rm yr}$, 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.Comment: 10 pages, 8 figures, to appear in Ap

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