High-energy Astrophysics

A core-collapse supernova explosion is a massive explosion that occurs at the final moment of a massive star's life. Its momentary brightness can rival that of its host galaxy, which has led to numerous observations throughout history. However, the explosion mechanism has not yet been fully elucidated. It has become clear that compact objects such as neutron stars or black holes are left behind after the supernova explosion and that neutrinos, produced in numbers as large as 10⁵⁸, seem to play an essential role.

I am advancing research using neutrino radiation hydrodynamics simulations that combine neutrino radiation transport and fluid dynamics to elucidate the explosion mechanism. Executing such calculations requires more computational power than personal computers can provide, so I am utilizing supercomputers.

Gamma-ray bursts (GRBs) are among the most violent explosions in the universe. It is known that GRBs can be classified into two types: those with long durations are believed to occur at the end of a massive star's life, while the shorter ones are thought to result from the merger of two neutron stars or a neutron star and a black hole. Although it's understood that GRBs are produced by ultra-relativistic outflows (jets), how these jets are formed remains a significant mystery. Furthermore, what happens as these jets bore through the star is also unclear. I am pursuing research through various approaches to unravel these mysteries.

Neutron stars are incredibly dense objects, cramming mass greater than that of the sun into a mere 10-kilometer radius. They form from the remnants of supernova explosions, meaning a thorough understanding of their genesis necessitates tracing the transition from supernova to neutron star. My research focuses on exploring this transformation through simulations of supernova explosions.

Neutron stars are known for their incredibly strong magnetic fields, typically around 10¹² gauss, compared to the Earth's surface magnetic field of approximately 0.5 gauss. Those with even more extreme magnetic fields are referred to as magnetars, the most powerful magnets in the universe. My research includes studying the effects and phenomena driven by these intense magnetic fields.

The vast array of elements in the universe are forged within the cores of stars and scattered across space by the cataclysmic force of supernova explosions. Even the carbon and oxygen that constitute our bodies have stellar origins. I am engaged in researching how these elements come to be and the intricate process of element formation that unfolds within the fiery crucibles of supernovae.

The earliest stars formed in the universe are referred to as Population III stars. Given the drastically different conditions of their formation compared to now, it's thought that their characteristics, such as mass, significantly diverge from the stars we observe in our vicinity. I am dedicated to exploring these primordial stars and the celestial phenomena of the early universe by studying the gravitational collapses and explosive events marking the end of their existence.

Multimessenger astronomy marks a new era in the 21st century, expanding beyond the traditional electromagnetic observations to embrace a variety of cosmic messengers such as neutrinos and gravitational waves. My work is especially centered on exploring supernova explosions through this innovative lens, allowing us to delve into the innermost secrets of stars.