中性子星連星系合体・超新星のインパクト：重元素の起源とニュートリノ振動
梶野 敏貴
国立天文台
日時：2018年02月02日（金） 10:30-
場所：大学院講義室（総合研究棟7階745号室）
地上に存在するウランなどの重元素は速い中性子捕獲過程（ｒ過程）により作られる。ｒ過程の候補天体である超新星爆発と中性子星連星 系合体との間では長年論争が繰り広げられてきた。今夏ついに中性子 星連星系が合体して重力波・ガンマ線・可視赤外線などを放出する様子を重力波望遠鏡・宇宙ガンマ線観測衛星・光赤外線地上望遠鏡等で捉える ことに成功し、中性子星連星系の合体がｒ過程元素合成のサイトである可能性が観測的に強く示唆された。マルチメッセンジャー天文学・宇宙 核物理学の幕開けである。本報告では両天体でのｒ過程元素合成計算に加え、 我々の銀河の化学・動力学的進化計算を行うことで重元素の起源の謎に総合的に迫る。また超新星元素合成におけるニュートリノ振動の重要性についても解説する。GW170817 was really an event of the century that has opened the window to the frontier of multi-messenger astronomy and astrophysics. Gravitational waves from most likely the merging neutron stars were detected by LIGO-Virgo collaboration,and GRB was observed in Fermi-GBM. Although the emission line from specific r-process elements were detected, bulk energy in observed optical and near-infrared emissions are consistent with those from radiative decays of r-process nuclei which are predicted theoretically. Neutrinos were not detected because of their too low flux from GW170817 that occurred at a distance 0.13 Gly away. We now await a nearby GW event (probably once per one thousand years in our Milky Way) for spectroscopic observation of still unidentified r-process elements from neutron star mergers (NSMs). Not only the NSMs but core-collapse supernovae (of both magneto-hydrodynamic jet supernovae; MHD Jet-SNe, and neutrino-driven wind supernovae; ν-SNe) are viable candidates for the r-process sites. NSMs could not contribute to the early Galaxy for cosmologically long merging time-scale for slow GW radiation, while MHD Jet-SNe can explain the “universality” in the observed abundance pattern in metal poor stars. Nevertheless, NSM like GW170817 is undoubtedly a possible nucleosynthetic site for the solar-system r-process abundance. We would like to propose a novel solution to this twisted problem by carrying out both NSM and SN r-process nucleosynthesis calculations and numerical simulation of Galactic chemo-dynamical evolution. We will also discuss the impact of the SN nucleosynthesis on the physics of neutrino oscillations including MSW, collective and vacuum oscillations.