早稲田大学 理工学術院 先進理工学部 物理学科・応用物理学科




山田 章一 [教授] dummy_photo
homepage http://www.heap.phys.waseda.ac.jp/index.html
専門分野 宇宙物理






Shoichi Yamada [Professor] dummy_photo
homepage http://www.heap.phys.waseda.ac.jp/index.html
research field Neutrino and gravitational wave astronomy of massive-star collapse
research keywords
High energy astrophysics
Mechanism of collapse-driven supernovae and physics of hadronic matter at high densities
Neutrinos and gravitational waves from the formation of black holes and neutron stars

Research Profiles (at Faculty of Science and Engineering)

Research Profiles (Elsevier SciVal Experts)

Neutrino and gravitational wave astronomy of massive-star collapse

Gravitational collapse is the common fate of massive stars, followed by the formation of compact objects such as neutron stars and black holes. This gravitational collapse is initiated by the central core of a massive star, which is surrounded by massive envelopes and cannot be probed by electromagnetic waves. The actual conditions in these regions have been inferred over the years based on indirect evidence for example, nucleosynthetic yields. This may have already changed dramatically, however, with multiple terrestrial detectors of neutrinos and gravitational waves now deployed, operating, and poised to detect the next event.

Since neutrinos and gravitational waves interact very weakly with matter, they escape the central core unhindered, carrying information on the environment where the emissions originate. Although the very weakness of the interactions once constituted a major challenge for experimentalists, this is no longer the case. The ball is once again in the theoreticians’ court. Needed now are quantitative predictions to compare against observations. As the detection of neutrinos from SN1987A clearly demonstrates, neutrinos from core-collapse supernovae and the proto-neutron stars that form subsequently should be among the primary targets in neutrino astronomy.

Also emerging now is gravitational-wave astronomy. Over the last decade, we have witnessed significant progress in the international network of detectors, including LIGO, VIGRO, GEO600, TAMA300, and AIGO, and the direct detection of gravitational waves from astrophysical events should soon be possible.
Promising sources would include a massive star collapse, particularly within our own galaxy.

Over the years, in large-scale numerical simulations, we have demonstrated that the detection of neutrinos and/or gravitational waves emitted by the gravitational collapse of massive stars will convey much information not just about what goes on under the thick veil of the massive envelopes, but about the properties of dense and hot baryonic matter. In so doing we have pointed out the importance of black-hole-forming events, which are still putative but, if observed, will provide invaluable and otherwise inaccessible information. In fact, the neutrino bursts from the optically silent collapses of massive stars have unique characteristics that distinguish them from ordinary supernova neutrinos; hence, they can be used not just as indicators of black hole formation, but as probes of dense baryonic matter. It is fascinating that such an event may be confirmed by the detection of “the disappearance of one of the numerous massive stars” monitored optically as another proposed initiative. If the progenitor star is rotating, we will also have the chance to detect the event via gravitational waves.

Four snapshots of our 3D supernova simulation. The length of each side of the plot corresponds to 1000 km. The entropy distributions are shown. The second and fourth quadrants of each panel show the surface of the shock wave. The high entropy bubbles (colored red) in the section cut by the $ZX$ plane are displayed in the first and third quadrants. The insets show gravitational waveforms from anisotropic neutrino emissions.