Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session CG: Mini-Symposium on Nuclear Physics in Stars II |
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Chair: Charles Horowitz, Indiana University Room: Kings 2 |
Thursday, October 15, 2009 9:00AM - 9:30AM |
CG.00001: Neutrino Oscillation in Supernovae and Its Influence on Nucleosynthesis Invited Speaker: During a supernova (SN) explosion, a huge amount of neutrinos are emitted from a proto-neutron star. These neutrinos change their flavors by neutrino oscillation. In the O/C and He/C layers, the flavor change occurs by the MSW effect and, therefore, the average energies of $\nu_e$ and $\bar{\nu}_e$ increase. The increase in the average neutrino energies enhance the effect of charged-current neutrino-nucleus reactions so that the yields of light elements produced through the $\nu$-process increase. Recently, the flavor change by neutrino self-interaction has been discussed. Since the flavor change occurs in the innermost region of SN ejecta, it could affect neutrino-nucleus reactions in such a deep region. I would like to talk about neutrino oscillations in SNe, including the MSW effect and neutrino self-interaction, and the change of neutrino energy spectra in SNe. I also would like to discuss the influence of the neutrino oscillation on the nucleosynthesis of light elements produced through the $\nu$-process and heavy elements produced in the innermost region of the SN ejecta. [Preview Abstract] |
Thursday, October 15, 2009 9:30AM - 9:45AM |
CG.00002: Quantum Coherence of Relic Neutrinos Chad Kishimoto, George Fuller The cosmic neutrino background (i.e., the relic neutrinos) last scattered in the early universe when the photon-baryon plasma was very hot, around the epoch of big bang nucleosynthesis. At this last scattering surface the neutrinos are largely in flavor eigenstates. We discuss the implications of this fact on cosmology and cosmological limits on neutrino parameters. [Preview Abstract] |
Thursday, October 15, 2009 9:45AM - 10:00AM |
CG.00003: ABSTRACT WITHDRAWN |
Thursday, October 15, 2009 10:00AM - 10:15AM |
CG.00004: Neutrino-Induced Reactions on Ni and Fe Isotopes and Nucleosynthesis in Stars Toshio Suzuki, Michio Honma, Koji Higashiyama, Takashi Yoshida, Toshitaka Kajino, Takaharu Otsuka, Hideyuki Umeda, Ken'ichi Nomoto Neutrino-induced reactions on Ni and Fe isotopes are investigated based on new shell model Hamiltonians for $fp$-shell, GXPF1. Spin and magnetic properties of nuclei have been considerably improved by the Hamiltonians, where important roles of tensor interaction on shell evolutions are properly taken into account. Charge-exchange reactions on $^{56}$Fe induced by DAR neutrinos is investigated by using Gamow-Teller strength obtained by the new Hamiltonian, GXPF1J. The observed cross section is shown to be consistent with the observation. The Gamow-Teller strength in $^{56}$Ni is found to be more spread compared to previous calculations and result in a considerably large branching ratio for the proton knock-out channel. This leads to the enhancement of the production yields of heavy elements such as $^{55}$Mn and $^{59}$Co in population III stars for the new Hamiltonian [1]. The electron capture reactions on $^{56}$Ni, neutrino-induced reactions on $^{52}$Fe and the production of elements such as $^{51}$V in supernovae will be also discussed. \\[4pt] [1] T. Suzuki et al., Phys. Rec. C79, 061603(R) (2009). [Preview Abstract] |
Thursday, October 15, 2009 10:15AM - 10:30AM |
CG.00005: Breakup of proton-rich nuclei $^{24}$Si and $^{23}$Al at intermediate energies for reaction rates in explosive H-burning in novae and X-ray bursts A. Banu, L. Trache, R.E. Tribble, B. Roeder, E. Simmons, N. Orr et al., M. Chartier et al., R. Lemmon et al., W. Catford et al., M. Freer, F. Carstoiu et al., M. Horoi, A. Bonaccorso We present the use of one-proton-removal reactions of loosely bound nuclei at intermediate energies as an indirect method in nuclear astrophysics, with particular reference to the results of a GANIL experiment with a cocktail beam around $^{23}$Al at 50 MeV/nucleon. Momentum distributions of the core fragments, inclusive and in coincidence with gamma rays, from which we determine configuration mixing in the structure of the ground states of the projectile nuclei, were measured. The method has the advantage that it can be used for beams of low quality, such as cocktail beams, and intensities as low as a few pps. These breakup reactions provide information on H-burning reaction rates for $^{22}$Mg(p,$\gamma )^{23}$Al and $^{23}$Al(p,$\gamma)^{24}$Si, important in novae and X-ray bursts. [Preview Abstract] |
Thursday, October 15, 2009 10:30AM - 10:45AM |
CG.00006: A Study of the $^{30}$S($\alpha,p$)$^{33}$Cl Reaction Rate C.M. Deibel, C.L. Jiang, B.P. Kay, H.Y. Lee, R.C. Pardo, K.E. Rehm, C. Ugalde, A. Woodard, J.M. Figueira, S.T. Marley, N.R. Patel, M. Paul, A. Wuosmaa The $^{30}$S($\alpha,p$)$^{33}$Cl reaction rate has major implications for x-ray bursts (XRBs). No experimental information exists for this reaction rate, though XRB models have shown that it affects final isotopic abundances and the total energy output.\footnote{A. Parikh {\it et al.}, ApJ SS {\bf178}, 110 (2008).} This rate may also influence XRB observables such as the structure of double-peaked luminosity curves\footnote{J.L. Fisker {\it et al.}, ApJ {\bf608}, L61 (2004).} and the composition of the neutron star crust.\footnote{H. Schatz and K.E. Rehm, NPA {\bf777}, 601 (2006).} We have studied the time-inverse reaction $p$($^{33}$Cl,$^{30}$S)$\alpha$ at ATLAS using a radioactive $^{33}$Cl beam. The residual $^{30}$S nuclei were detected at the focal plane of the split-pole spectrograph, which was used in gas-filled mode, in coincidence with the $\alpha$ particles, which were detected in a double-sided Si detector. The experimental results and conclusions about the impact on XRB nucleosynthesis will be discussed. [Preview Abstract] |
Thursday, October 15, 2009 10:45AM - 11:00AM |
CG.00007: Nucleosynthesis of Nickel-56 from Gamma-Ray Burst Accretion Disks Rebecca Surman, Nicole Sabbatino, Gail McLaughlin Observational evidence suggests that long-duration gamma-ray bursts (GRBs) are linked to the collapse of massive, rotating stars. One piece of this evidence is the observation of supernova light curves in the afterglow of a number of long-duration GRBs. Since the radioactive decay of Nickel-56 drives the light curves of ordinary core-collapse supernovae, long-duration GRBs must also copiously produce Nickel-56. This nickel may be produced in explosive burning, as in ordinary supernovae, or in outflows from the central object of the GRB---an accretion disk around a stellar-mass black hole. Here we examine the latter mechanism, by investigating outflows from a range of steady state accretion disk models. We find that significant amounts of Nickel-56 are produced over a wide range of disk and outflow parameter space. We discuss the influence of disk accretion rate, outflow entropy, outflow timescale, initial disk position, and neutrino-nucleon interactions on the mass fraction of Nickel-56 produced. [Preview Abstract] |
Thursday, October 15, 2009 11:00AM - 11:15AM |
CG.00008: Galactic Chemical Evolution and Origin of r-Process Elements Yuhri Ishimaru, Shinya Wanajo Metal-poor stars record enrichment history of the Galaxy at the early epoch. Observations of these stars show large star-to-star scatters in their abundances of neutron-capture elements. This indicates that these stars were enriched by only one or a few supernovae (SNe), since the inter-stellar medium had not been fully mixed when they were formed. Thus, the huge dispersions suggest that r-process yields are highly dependent on the SN progenitor mass, although the astrophysical site of r-process remains still uncertain. We attempt to determine the origin of r-process elements from the point of view of chemical enrichment of the Galaxy. We construct an inhomogeneous chemical evolution model on the assumption of SN induced star formation. Various stellar mass ranges are assumed for the site of r-process, and the predicted distributions of stellar chemical components are compared with observational data including those collected at the SUBARU Telescope. [Preview Abstract] |
Thursday, October 15, 2009 11:15AM - 11:30AM |
CG.00009: Elucidating the Properties of Dense Matter from Starquakes in Neutron Star Crusts Andrew Steiner The recent observation of quasi-periodic oscillations in giant flares produced in highly magnetized neutron stars offers a unique opportunity to constrain the properties of the neutron star crust. The frequencies, some of which are thought to be normal modes of oscillation of the neutron star crust, can be measured to few percent accuracy. I will show that the normal mode frequencies are quite sensitive to the nuclear physics aspects of the crust, in particular, to the nuclear symmetry energy. This promises to be an important constraint on the nuclear symmetry energy which is complementary to constraint obtained by the determination of the neutron skin thickness of lead at Jefferson Lab. [Preview Abstract] |
Thursday, October 15, 2009 11:30AM - 11:45AM |
CG.00010: Nuclear limits on gravitational waves from neutron stars Plamen Krastev, Aaron Worley, Bao-An Li Neutron stars are among the possible sources emitting gravitational waves (GWs) with a strain-amplitude dependent upon star's quadrupole moment, rotational frequency, and distance from detector. We show that the gravitational wave strain amplitude depends strongly on the equation of state of neutron-rich stellar matter. Applying an equation of state with symmetry energy constrained by recent nuclear laboratory data, we set an upper limit on the strain amplitude of GWs produced by neutron stars. Implications will be discussed. [Preview Abstract] |
Thursday, October 15, 2009 11:45AM - 12:00PM |
CG.00011: Nuclear Equation of State in the Presence of a Strong Magnetic Field Grant Mathews, In-Saeng Suh Strong magnetic fields ($\sim 10^{17}$ G) can exist in the interiors of some neutron stars (magnetars). Such fields can modify the nuclear equation of state through effects of the magnetic pressure and the population of Landay levels by the electrons and nucleons. In this work magnetic properties such as the magnetization and the susceptibility of magnetar nuclear matter are calculated in the framework of relativistic Hartree mean field theory in which the baryons (neutrons, $n$, and protons, $p$) interact via the exchange of scalar $\sigma$ and vector $\omega, \rho$ mesons. We find that the magnetization undergoes large de Haas van Alphen oscillations. The magnetic susceptibility then becomes unstable to the formation of {\it magnetic domains}. This magnetic domain formation can affect the surface properties of magnetars. In particular, the energy released by domain formation is comparable to the observed episodic energy outbursts of soft gamma repeaters (SGRs) and Anoamlous X-ray Pulsars (AXPs) thought to result from magnetars. [Preview Abstract] |
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