Ryosuke Hirai's Homepage

Research Interests

Binary Stars

My main research interest is on binary stars, especially for high mass stars which explode as core-collapse supernova at the end of their lives. I have worked intensively on "ejecta-companion interaction", which is the effect of supernova ejecta colliding with a companion star. I have also studied the evolution of binary systems which can reproduce the observed features of a particular supernova iPTF13bvn.

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Hydrodynamical simulations of ejecta-companion interaction (Hirai, Podsiadlowski & Yamada 2018, Hirai, Sawai & Yamada 2014).
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Binary evolution simulations for the progenitor of iPTF13bvn (Hirai & Yamada 2015, Hirai 2017a,Hirai 2017b).

Numerical Techniques

Numerical computation is almost inevitable when studying quantitative behaviours of astrophysical phenomena. But we usually have limited computer power, which prevents us from carrying out simulations of the desired resolution. I have investigated how we can improve the computational efficiency of self-gravitational hydrodynamical simulations so that we can speed up simulations.

Test calculation of colliding stars using our "Hyperbolic Self-Gravity Solver" (Hirai, Nagakura, Okawa & Fujisawa 2016).