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  1. Neutrinos and nucleosynthesis of elements

  2. Neutrino Production Associated with Late Bumps in Gamma-Ray Bursts and Potential Contribution to Diffuse Flux at IceCube

    IceCube has detected many TeV–PeV neutrinos, but their astrophysical origins remain largely unknown. Motivated by the observed late-time X-ray/optical bumps in some gamma-ray bursts (GRBs), we examine the correlation between IceCube neutrinos and GRBs allowing delayed neutrinos ~days after the prompt gamma-rays. Although we have not found any definitive correlation, up to ~10% of the events observed so far at IceCube may have been neutrinos produced by the late-time GRB activities at ~1 day. Assuming a connection between some IceCube events and the late GRB bumps, we show in a model-independent way that GRB sites capable of producing late ~PeVmore » neutrinos should be nonrelativistic or mildly relativistic. We estimate the diffuse neutrino flux from such sources and find that they can possibly account for a few IceCube events. Future observations of high-energy neutrinos and late-time GRB afterglows can further test the above proposed connection.« less
  3. Neutrino signal from proto-neutron star evolution: Effects of opacities from charged-current–neutrino interactions and inverse neutron decay

    In this work, we investigate the impact of charged-current–neutrino processes on the formation and evolution of neutrino spectra during the deleptonization of proto-neutron stars. To this end we develop the full kinematics of these reaction rates consistent with the nuclear equation of state, including weak magnetism contributions. This allows us to systematically study the impact of inelastic contributions and weak magnetism on the $$ν_e$$ and $$\bar{ν}_e$$ luminosities and average energies. Furthermore, we explore the role of the inverse neutron decay, also known as the direct Urca process, on the emitted spectra of $$\bar{ν}_e$$. This process is commonly considered in themore » cooling scenario of cold neutron stars but has so far been neglected in the evolution of hot proto-neutron stars. We find that the inverse neutron decay becomes the dominating opacity source for low-energy $$\bar{ν}_e$$. Accurate three-flavor Boltzmann neutrino transport enables us to relate the magnitude of neutrino fluxes and spectra to details of the treatment of weak processes. This allows us to quantify the corresponding impact on the conditions relevant for the nucleosynthesis in the neutrino-driven wind, which is ejected from the proto-neutron star surface during the deleptonization phase.« less
  4. Multimessenger asteroseismology of core-collapse supernovae

    In this work we investigate correlated gravitational wave and neutrino signals from rotating core-collapse supernovae with simulations. Using an improved mode identification procedure based on mode function matching, we show that a linear quadrupolar mode of the core produces a dual imprint on gravitational waves and neutrinos in the early post-bounce phase of the supernova. The angular harmonics of the neutrino emission are consistent with the mode energy around the neutrinospheres, which points to a mechanism for the imprint on neutrinos. Thus, neutrinos carry information about the mode amplitude in the outer region of the core, whereas gravitational waves probemore » deeper in. We also find that the best-fit mode function has a frequency bounded above by ~420 Hz , and yet the mode’s frequency in our simulations is ~15 % higher, due to the use of Newtonian hydrodynamics and a widely used pseudo-Newtonian gravity approximation. This overestimation is particularly important for the analysis of gravitational wave detectability and asteroseismology, pointing to limitations of pseudo-Newtonian approaches for these purposes, possibly even resulting in excitation of incorrect modes. In addition, mode frequency matching (as opposed to mode function matching) could be resulting in mode misidentification in recent work. Lastly, we evaluate the prospects of a multimessenger detection of the mode using current technology. The detection of the imprint on neutrinos is most challenging, with a maximum detection distance of ~ 1 kpc using the IceCube Neutrino Observatory. The maximum distance for detecting the complementary gravitational wave imprint is ~ 5 kpc using Advanced LIGO at design sensitivity.« less
  5. Collisional flavor instability in dense neutrino gases

  6. Finding the Remnants of the Milky Way's Last Neutron Star Mergers

    The discovery of a binary neutron star merger (NSM) through both its gravitational wave and electromagnetic emission has revealed these events to be key sites of $$r$$-process nucleosynthesis. Here, we evaluate the prospects of finding the remnants of Galactic NSMs by detecting the gamma-ray decay lines from their radioactive $$r$$-process ejecta. We find that 126Sn, which has several lines in the energy range 415-695 keV and resides close to the second $$r$$-process peak, is the most promising isotope, because of its half-life $$t_{1/2}$$ = 2:30(14) 105 yr being comparable to the ages of recent NSMs. Using a Monte Carlo procedure,more » we predict that multiple remnants are detectable as individual sources by next-generation $$\gamma$$-ray telescopes which achieve sub-MeV line sensitivities of ~18-8-10-6$$\gamma$$ cm-2 s-1. However, given the unknown locations of the remnants, the most promising search strategy is a systematic survey of the Galactic plane and bulge extending to high Galactic latitudes. Individual known supernova remnants which may be mis-classi ed NSM remnants could also be targeted, especially those located outside the Galactic plane. Detection of a moderate sample of Galactic NSM remnants would provide important clues to unresolved issues such as the production of actinides in NSMs, properties of merging NS binaries, and even help distinguish them from rare supernovae as current Galactic $r-$process sources. We also investigate the diffuse flux from longer-lived nuclei (e.g. 182Hf) that could in principle trace the Galactic spatial distribution of NSMs over longer timescales, but find that the detection of the diffuse flux appears challenging even with next-generation telescopes.« less
  7. Physics of neutrino flavor transformation through matter–neutrino resonances

    In astrophysical environments such as core-collapse supernovae and neutron star–neutron star or neutron star–black hole mergers where dense neutrino media are present, matter–neutrino resonances (MNRs) can occur when the neutrino propagation potentials due to neutrino–electron and neutrino–neutrino for-ward scattering nearly cancel each other. We show that neutrino flavor transformation through MNRs can be explained by multiple adiabatic solutions similar to the Mikheyev–Smirnov–Wolfenstein mecha-nism. As a result, we find that for the normal neutrino mass hierarchy, neutrino flavor evolution through MNRs can be sensitive to the shape of neutrino spectra and the adiabaticity of the system, but such sensitivity is absentmore » for the inverted hierarchy.« less

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