Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session 1WB: Nuclear and Neutrino Astrophysics I |
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Chair: Chris Fryer, Los Alamos National Laboratory Room: Hilton Hotel Mesa B |
Tuesday, November 2, 2010 3:00PM - 3:30PM |
1WB.00001: Black Hole Formation in Failing Core-Collapse Supernovae Invited Speaker: The cores of massive stars collapse to protoneutron stars, forming, at core bounce, a hydrodynamic shock that initially travels outward in mass and radius, but soon stalls, needing revival by the supernova mechanism. If the latter lacks efficacy, the protoneutron star may reach its maximum mass before an explosion is launched, leading to a second stage of gravitational collapse resulting in the formation of a black hole. Under special, yet to be determined conditions, a black hole -- accretion torus system may form in such failing supernovae and act as the engine of a long gamma-ray burst. I present results from new 1.5D (spherical symmetry plus rotation) and 3D general-relativistic simulations of stellar collapse and postbounce supernova evolution towards black hole formation in massive rotating and nonrotating progenitor stars. I demonstrate that there is no direct black hole formation without protoneutron-star phase in ordinary massive stars and establish the systematics of black hole forming collapse events with progentior mass, metallicity, rotation, and neutrino heating efficiency based on an extensive set of 1.5D simulations. I go on to present the first 3D simulations of black hole forming core-collapse events that track the evolution from the onset of collapse, through the protoneutron star phase and protoneutron star collapse to multiple tens of milliseconds after the appearance of the black hole horizon. [Preview Abstract] |
Tuesday, November 2, 2010 3:30PM - 4:00PM |
1WB.00002: Detection of Neutrinos from Galactic and Cosmic Supernovae Invited Speaker: Detecting neutrinos is the key to understanding core-collapse supernovae, but this is notoriously difficult due to the small interaction cross section of neutrinos and the low frequency of supernovae. The prospects for detecting Galactic supernovae depend almost completely on the probability of a fluctuation from the low supernova rate; the detection aspects are largely under control. The prospects for detecting Cosmic supernovae instead depend almost completely on the detection aspects, especially regarding reducing detector backgrounds; the supernova rate and neutrino flux of the universe are now rather well measured or predicted. After decades of effort and patience, we have good reasons to anticipate that detecting supernova neutrinos is within reach. [Preview Abstract] |
Tuesday, November 2, 2010 4:00PM - 4:30PM |
1WB.00003: Neutrino Oscillations In Supernovae Invited Speaker: Neutrinos play very important roles in core-collapse supernovae as they constitute 99\% of the total energy budget of the collapse. Because the charged-current neutrino processes are flavor dependent, neutrino flavor transformation or neutrino oscillations, depending on where it occurs and how it occurs, can also be important to supernova dynamics, supernova nucleosynthesis, etc. Tracking neutrino oscillations in supernovae is more difficult than solving the solar neutrino problem because: (1) both neutrino mass-squared differences are important, (2) matter density profiles are dynamical and far from smooth, and (3) flavor transformation of different neutrinos can become coupled. The last difficulty was not widely appreciated until recently, and rapid progress is made towards a full understanding of this issue. It is now clear that neutrino oscillations near the proto-neutron star can become collective because of the large neutrino fluxes. A clear signature of spectral swaps/splits can show up in supernova neutrino signals if this is the case. The onset radius of collective neutrino oscillations has an nontrivial, i.e. not well understood, dependence on the initial neutrino energy spectra at the neutrino sphere(s), but has a rather simple relation with neutrino luminosities and the neutron star radius. [Preview Abstract] |
Tuesday, November 2, 2010 4:30PM - 5:00PM |
1WB.00004: COFFEE BREAK
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Tuesday, November 2, 2010 5:00PM - 5:30PM |
1WB.00005: Neutron rich matter, neutron stars, and their crusts Invited Speaker: Neutron rich matter can be studied with an extraordinary variety of new tools from radioactive beam accelerators to multi-messenger astronomical observatories. We describe the dense matter in neutron star crusts with large-scale molecular dynamics simulations. We present results for how white dwarf and neutron stars freeze and for many properties of the resulting solid stars including thermal conductivity, shear viscosity, and breaking stress. We use these results to predict electromagnetic, neutrino, and gravitational wave radiations of neutron stars. [Preview Abstract] |
Tuesday, November 2, 2010 5:30PM - 6:00PM |
1WB.00006: Drilling into a neutron star with X-ray transients Invited Speaker: Over the last decade, advances in X-ray astronomy have greatly improved our knowledge of nuclear-powered phenomena on accreting neutron stars, such as type I X-ray bursts, superbursts, and cooling from quiescent neutron star transients. Spurred by these observations, theorists are beginning to reconstruct the nuclear evolution of accreted matter as it journeys from the low-density, proton-rich photosphere to the high-density, neutron-rich core. Knowledge of the interior thermal and compositional structure of the crust is important for understanding the detectability of gravitational wave emission from crust ``mountains,'' the strength of neutrino cooling in the core, the magnetic field evolution of the star, and the ignition of bursts at low mass accretion rates. These phenomena are potentially useful for constraining the dense matter equation of state. In this talk, I shall review our current understanding of the reactions in the neutron star crust. I shall then highlight new observations of cooling neutron star transients and what they reveal about the distribution of nuclei in the crust and the neutrino emissivity of the core. The rapidly cooling lightcurves of neutron star transients imply a highly conductive, cool crust, but the inferred ignition depths of superbursts, if powered by $\mathrm{^{12}C + ^{12}C}$ fusion, require a hot crust. I will discuss the tension between these phenomena and possible resolutions. [Preview Abstract] |
Tuesday, November 2, 2010 6:00PM - 6:30PM |
1WB.00007: Carbon Burning in the Universe and the Laboratory Invited Speaker: Carbon burning is a crucial process in stellar evolution. Due to its complicated reaction mechanism, there is great uncertainty in the reaction rate which limits our understanding of various stellar objects, such as massive stars, type Ia supernovae, and superbursts. In this talk, the challenges in the study of carbon burning will be reviewed, and an outlook for future experiments will be provided. [Preview Abstract] |
Tuesday, November 2, 2010 6:30PM - 7:00PM |
1WB.00008: Recent experiments related to explosive nuclear burning Invited Speaker: Explosive stellar environments such as novae, supernovae, and x- ray bursts are currently among the most exciting topics in nuclear astrophysics. Reactions on unstable nuclei play a crucial role in the energy generation and nucleosynthesis due to the high temperatures and short reaction time scales in these events, but substantial uncertainties often exist in nuclear reaction rates on unstable nuclei resulting from limited experimental data. In recent years some remarkable developments in radioactive ion beam production and experimental techniques have allowed many key reaction rates to be experimentally determined with reasonable accuracy for the first time. Experimental methods, results, and some remaining challenges will be outlined in this presentation. [Preview Abstract] |
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