Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session R1: Neutron Stars and the Dense Matter Equation of State |
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Sponsoring Units: DNP DAP Chair: Charles Horowitz, Indiana University, Bloomington Room: Grand A |
Monday, May 2, 2011 1:30PM - 2:06PM |
R1.00001: Hans A. Bethe Prize Talk: Neutron stars and stellar collapse: the physics of strongly interacting Fermi systems Invited Speaker: The talk will touch on a number of themes in the application of many-body theory to neutron stars and stellar collapse. One of these will be the composition and equation of state of nuclear matter. Specific topics will include nuclei in neutron stars, superfluidity and superconductivity of nuclear matter, and inhomogeneous phases of nuclear matter. A second major theme will be neutrino processes in dense matter: neutrino emission is the most powerful cooling mechanism for young neutron stars, and rates of neutrino processes are a key ingredient in simulations of stellar collapse. [Preview Abstract] |
Monday, May 2, 2011 2:06PM - 2:42PM |
R1.00002: Astrophysical Measurement of the Ultradense Matter Equation of State Invited Speaker: Neutron stars are the densest objects in the universe and may contain hyperon-dominated matter, condensed mesons, or even deconfined or strange quark matter. Because of their low temperatures and high chemical potentials, the physical conditions in their interiors differ greatly from the dense conditions of the early universe or those achieved at hadron colliders. This region of the QCD phase diagram can best be probed through astrophysical observations that measure the masses and radii of neutron stars. I will discuss how we can break degeneracies in the measurements of neutron star properties by combining recent developments in our understanding of their atmospheres with observations of multiple spectroscopic phenomena from X-ray binaries. I will present unique measurements of the masses and radii of a number of neutron stars in low-mass X-ray binaries and show the equations of state of neutron star matter that are compatible with these observations. These measurement constrain, for the first time, the pressure of cold matter above nuclear saturation density and offer tantalizing evidence for new degrees of freedom at ultrahigh densities. [Preview Abstract] |
Monday, May 2, 2011 2:42PM - 3:18PM |
R1.00003: Determination of the Neutron Star Equation of State from Astrophysical Measurement Invited Speaker: Recent observations of cooling neutron stars and of photospheric radius expansions in X-ray bursters are used to simultaneously estimate their masses and radii. Although the observational uncertainties for these sources are large, they nevertheless snugly constrain the mass-radius relation and the underlying equation of state. The results of a Bayesian analysis using a parametrized equation of state are discussed. The results for the low-density equation of state are consistent with those deduced from recent nuclear physics estimates of pure neutron matter. Furthermore, the deduced nuclear incompressibility is surprisingly compatible with nuclear systematics and experiment. The density dependence of the nuclear symmetry energy is predicted to be relatively small, leading to correspondingly small values for the predicted neutron skin thickness of lead and for the radii of 1.4 M$_\odot$ stars. The high-density equation of state is predicted to stiffen, however, and the estimated neutron star maximum mass, to 90\% confidence, is greater than 1.85 solar masses. I also will discuss recent observations of the cooling of the neutron star in the Cas A supernova remnant, which provides not only strong evidence for the existence of both neutron superfluidity and proton superconductivity, but also a tight measurement of the $^3$P$_2$ neutron gap. [Preview Abstract] |
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