Toshikazu Shigeyama

TL;DR: In this paper, the authors reported the discovery of transient optical emission in the error box of the gamma-ray burst GRB980425, the light curve of which was very different from that of previous optical afterglows associated with Gamma-ray bursts.

TL;DR: The discovery of the unusual supernova SN1998bw, and its possible association with the γ-ray burst GRB 9804251,2,3, provide new insights into the explosion mechanism of very massive stars and the origin of some classes of gamma-ray bursts.

TL;DR: The discovery of the peculiar supernova (SN) 1998bw and its possible association with the gamma-ray burst (GRB) 980425$ 1,2,3} provides new clues to the understanding of the explosion mechanism of very massive stars and to the origin of some classes of gamma ray bursts.

TL;DR: In this article, the prepeak smooth rise and broad peak of the light curve are well modeled by assuming some mixing of Ni-56 into the hydrogen-rich envelope and of hydrogen into the core.

TL;DR: In this article, it was shown that the secondary brightening and subsequent decay of the light curve can be explained by the radioactive decay of 56Co; combined with the early spectrum, this suggests that the progenitor may have been a red supergiant with an unusually thin hydrogen-rich envelope.