Progenitor Model of SN 1987A Based on the Slow Merger Scenario: Impacts of the Envelope Rotation

Evolutionary properties of Sk -69{\deg}202, the progenitor of SN 1987A, is investigated. We have started with revisiting some scenarios proposed so far. We found that the rotation induced mixing is too weak to realize the required strong mixing, and also that the envelope mass enhancement due to binary interactions only is not enough to keep the deflated envelope until core collapse. Thus we consider the slow merger scenario proposed by Ivanova et al., expecting both of the strong mixing and the envelope mass enhancement to occur. In addition to the two effects, acceleration of the envelope spin is taken into account in our simplified 1D model. We show observational constraints of the red-to-blue evolution at 2x10^4 yr before core collapse, the total mass and the position in the HR diagram at collapse, and the envelope chemical abundances of He and CNO elements are well reproduced. Moreover the mass lost to eject a plausible amount of angular momentum, ~3x10^54 erg sec, is found to be too large to sustain a blue envelope. This indicates that an efficient reduction of angular momentum via disk-like ejection has to be taken place after the stellar merger.