13 research outputs found
Statistical theory of thermal evolution of neutron stars
Thermal evolution of neutron stars is known to depend on the properties of
superdense matter in neutron star cores. We suggest a statistical analysis of
isolated cooling middle-aged neutron stars and old transiently accreting
quasi-stationary neutron stars warmed up by deep crustal heating in low-mass
X-ray binaries. The method is based on simulations of the evolution of stars of
different masses and on averaging the results over respective mass
distributions. This gives theoretical distributions of isolated neutron stars
in the surface temperature--age plane and of accreting stars in the photon
thermal luminosity--mean mass accretion rate plane to be compared with
observations. This approach permits to explore not only superdense matter but
also the mass distributions of isolated and accreting neutron stars. We show
that the observations of these stars can be reasonably well explained by
assuming the presence of the powerful direct Urca process of neutrino emission
in the inner cores of massive stars, introducing a slight broadening of the
direct Urca threshold (for instance, by proton superfluidity), and by tuning
mass distributions of isolated and accreted neutron stars.Comment: 13 pages, 20 figure
NS 1987A in SN 1987A
The possible detection of a compact object in the remnant of SN 1987A
presents an unprecedented opportunity to follow its early evolution. The
suspected detection stems from an excess of infrared emission from a dust blob
near the compact object's predicted position. The infrared excess could be due
to the decay of isotopes like 44Ti, accretion luminosity from a neutron star or
black hole, magnetospheric emission or a wind originating from the spindown of
a pulsar, or thermal emission from an embedded, cooling neutron star (NS
1987A). It is shown that the last possibility is the most plausible as the
other explanations are disfavored by other observations and/or require
fine-tuning of parameters. Not only are there indications the dust blob
overlaps the predicted location of a kicked compact remnant, but its excess
luminosity also matches the expected thermal power of a 30 year old neutron
star. Furthermore, models of cooling neutron stars within the Minimal Cooling
paradigm readily fit both NS 1987A and Cas A, the next-youngest known neutron
star. If correct, a long heat transport timescale in the crust and a large
effective stellar temperature are favored, implying relatively limited crustal
n-1S0 superfluidity and an envelope with a thick layer of light elements,
respectively. If the locations don't overlap, then pulsar spindown or accretion
might be more likely, but the pulsar's period and magnetic field or the
accretion rate must be rather finely tuned. In this case, NS 1987A may have
enhanced cooling and/or a heavy-element envelope.Comment: 21 pages, 6 figures, to be published in Ap
Reaction rates and transport in neutron stars
Understanding signals from neutron stars requires knowledge about the
transport inside the star. We review the transport properties and the
underlying reaction rates of dense hadronic and quark matter in the crust and
the core of neutron stars and point out open problems and future directions.Comment: 74 pages; commissioned for the book "Physics and Astrophysics of
Neutron Stars", NewCompStar COST Action MP1304; version 3: minor changes,
references updated, overview graphic added in the introduction, improvements
in Sec IV.A.