Ko Nakamura

Systematic features of axisymmetric neutrino-driven core-collapse supernova models in multiple progenitors

We present an overview of two-dimensional (2D) core-collapse supernova simulations employing neutrino transport scheme by the isotropic diffusion source approximation. We study 101 solar-metallicity, 247 ultra metal-poor, and 30 zero-metal progenitors covering zero-age main sequence mass from 10.8M⊙ to 75.0M⊙. Using the 378 progenitors in total, we systematically investigate how the differences in the structures of these multiple progenitors impact the hydrodynamics evolution. By following a long-term evolution over 1.0 s after bounce, most of the computed models exhibit neutrino-driven revival of the stalled bounce shock at ∼ 200 - 800 ms postbounce, leading to the possibility of explosion. Pushing the boundaries of expectations in previous one-dimensional (1D) studies, our results confirm that the compactness parameter ξ that characterizes the structure of the progenitors is also a key in 2D to diagnose the properties of neutrino-driven explosions. Models with high ξ undergo high ram pressure from the accreting matter onto the stalled shock, which affects the subsequent evolution of the shock expansion and the mass of the protoneutron star under the influence of neutrino-driven convection and the standing accretion-shock instability. We show that the accretion luminosity becomes higher for models with high ξ, which makes the growth rate of the diagnostic explosion energy higher and the synthesized nickel mass bigger. We find that these explosion characteristics tend to show a monotonic increase as a function of the compactness parameter ξ.

Limits on Majoron-emitting double-β decays of 136Xe in the KamLAND-Zen experiment

We present limits on Majoron-emitting neutrinoless double-β decay modes based on an exposure of 112.3 days with 125 kg of 136Xe. In particular, a lower limit on the ordinary (spectral index n=1) Majoron-emitting decay half-life of 136Xe is obtained as T1/20νχ0>2.6×1024 yr at 90% C.L., a factor of five more stringent than previous limits. The corresponding upper limit on the effective Majoron-neutrino coupling, using a range of available nuclear matrix calculations, is 〈gee〉<(0.8-1.6)×10−5. This excludes a previously unconstrained region of parameter space and strongly limits the possible contribution of ordinary Majoron emission modes to 0νββ decay for neutrino masses in the inverted hierarchy scheme.

The red supergiant and supernova rate problems: Implications for core-collapse supernova physics

Mapping supernovae to their progenitors is fundamental to understanding the collapse of massive stars. We investigate the red supergiant problem, which concerns why red supergiants with masses

Impacts of rotation on three-dimensional hydrodynamics of core-collapse supernovae

\sim16

Self-similar solutions for the interaction of relativistic ejecta with an ambient medium

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Multimessenger signals of long-term core-collapse supernova simulations: synergetic observation strategies

30 M_\odot

SUPERNOVA NEUTRINO NUCLEOSYNTHESIS OF THE RADIOACTIVE 92Nb OBSERVED IN PRIMITIVE METEORITES

have not been identified as progenitors of Type IIP supernovae, and the supernova rate problem, which concerns why the observed cosmic supernova rate is smaller than the observed cosmic star formation rate. We find key physics to solving these in the compactness parameter, which characterizes the density structure of the progenitor. If massive stars with compactness above

ROLES OF SUPERNOVA EJECTA IN NUCLEOSYNTHESIS OF THE LIGHT ELEMENTS Li, Be, AND B

\xi_{2.5} \sim 0.2

Revisiting Impacts of Nuclear Burning for Reviving Weak Shocks in Neutrino-driven Supernovae

fail to produce canonical supernovae, (i) stars in the mass range

r-process nucleosynthesis in the MHD+neutrino-heated collapsar jet

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