162 research outputs found
Nuclear and High-Energy Astrophysics
There has never been a more exciting time in the overlapping areas of nuclear
physics, particle physics and relativistic astrophysics than today. Orbiting
observatories such as the Hubble Space Telescope, Rossi X-ray Timing Explorer
(RXTE), Chandra X-ray satellite, and the X-ray Multi Mirror Mission (XMM) have
extended our vision tremendously, allowing us to see vistas with an
unprecedented clarity and angular resolution that previously were only
imagined, enabling astrophysicists for the first time ever to perform detailed
studies of large samples of galactic and extragalactic objects. On the Earth,
radio telescopes (e.g., Arecibo, Green Bank, Parkes, VLA) and instruments using
adaptive optics and other revolutionary techniques have exceeded previous
expectations of what can be accomplished from the ground. The gravitational
wave detectors LIGO, LISA VIRGO, and Geo-600 are opening up a window for the
detection of gravitational waves emitted from compact stellar objects such as
neutron stars and black holes. Together with new experimental forefront
facilities like ISAC, ORLaND and RIA, these detectors provide direct,
quantitative physical insight into nucleosynthesis, supernova dynamics,
accreting compact objects, cosmic-ray acceleration, and pair-production in high
energy sources which reinforce the urgent need for a strong and continuous
feedback from nuclear and particle theory and theoretical astrophysics. In my
lectures, I shall concentrate on three selected topics, which range from the
behavior of superdense stellar matter, to general relativistic stellar models,
to strange quark stars and possible signals of quark matter in neutron stars.Comment: 52 pages, 43 figures; to appear in the Proceedings of the VIII
International Workshop on Hadron Physics, April 14-19, 2002, Rio Grande do
Sul, Brazi
Impact of Rotation-Driven Particle Repopulation on the Thermal Evolution of Pulsars
Driven by the loss of energy, isolated rotating neutron stars (pulsars) are
gradually slowing down to lower frequencies, which increases the tremendous
compression of the matter inside of them. This increase in compression changes
both the global properties of rotating neutron stars as well as their hadronic
core compositions. Both effects may register themselves observationally in the
thermal evolution of such stars, as demonstrated in this Letter. The
rotation-driven particle process which we consider here is the direct Urca (DU)
process, which is known to become operative in neutron stars if the number of
protons in the stellar core exceeds a critical limit of around 11% to 15%. We
find that neutron stars spinning down from moderately high rotation rates of a
few hundred Hertz may be creating just the right conditions where the DU
process becomes operative, leading to an observable effect (enhanced cooling)
in the temperature evolution of such neutron stars. As it turns out, the
rotation-driven DU process could explain the unusual temperature evolution
observed for the neutron star in Cas A, provided the mass of this neutron star
lies in the range of 1.5 to 1.9 \msun and its rotational frequency at birth was
between 40 (400 Hz) and 70% (800 Hz) of the Kepler (mass shedding) frequency,
respectively.Comment: Revised version, 7 pages 4 figures. To appear in Physics Letters
Constraints on the High-Density Nuclear Equation of State from Neutron Star Observables
Depending on the density reached in the cores of neutron stars, such objects
may contain stable phases of novel matter found nowhere else in the Universe.
This article gives a brief overview of these phases of matter and discusses
astrophysical constraints on the high-density equation of state associated with
ultra-dense nuclear matter.Comment: 16 pages, 11 figures, Contribution to Proceedings of the 3rd
International Workshop on Astronomy and Relativistic Astrophysics (IWARA),
3-6 October 2007, Joao Pessoa, Brazi
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