Issue |
A&A
Volume 381, Number 1, JanuaryI 2002
|
|
---|---|---|
Page(s) | 178 - 196 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20011499 | |
Published online | 15 January 2002 |
Slowly rotating superfluid Newtonian neutron star model with entrainment
1
Department of Mathematics, University of Southampton, Southampton SO17 1BJ, UK
2
Department of Physics, Saint Louis University, PO Box 56907, St. Louis, MO 63156-0907, USA
Corresponding author: R. Prix, r.prix@maths.soton.ac.uk
Received:
11
July
2001
Accepted:
25
October
2001
We develop a
formalism that can be used to model slowly rotating
superfluid Newtonian neutron stars. A simple two-fluid model is
used to describe the matter, where one fluid consists of the
superfluid neutrons that are believed to exist in the inner crust
and core of mature neutron stars, while the other fluid is a
charge neutral
conglomerate of the remaining constituents (crust nuclei,
core superconducting protons, electrons, etc.). We include
the entrainment effect, which is a non-dissipative interaction
between the two fluids whereby a momentum induced in one of the
fluids will cause part of the mass of the other fluid to be carried
along. The equations that describe rotational equilibria (i.e.
axisymmetric and stationary configurations) are approximated using
the slow-rotation approximation; an expansion in terms of
the rotation rates of the two fluids where only terms
up to second-order are kept. Our formalism allows the
neutrons to rotate at a rate different from that of the
charged constituents. For a particular equation of state
that is quadratic in the two mass-densities and relative
velocities of the fluids, we find
an analytic solution to the slow-rotation equations. This result
provides an elegant generalisation to the
two-fluid problem of the standard expressions for
the one-fluid polytrope .
The model equation of state includes entrainment and is general enough to
allow for realistic values for, say, mass and radius of the star. It
also includes a mixed term in the mass densities that can be related
to “symmetry energy” terms that appear in more realistic equations
of state. We use the analytic solution to explore how relative
rotation between the two fluids, the “symmetry energy” term, and
entrainment affect the neutron star's local distribution of particles, as
well as global quantities as
the Kepler limit, ellipticity, and moments of inertia.
Key words: stars: neutron / stars: rotation / hydrodynamics
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.