A progenitor model of SN 1987A based on the slow-merger scenario

Abstract

Even after elaborate investigations for 30 years, we still do not know well how the progenitor of SN 1987A has evolved. To explain unusual red-to-blue evolution, previous studies suggest that in a red giant stage either the increase of surface He abundance or the envelope mass was necessary. It is usually supposed that the He enhancement is caused by the rotational mixing, and the mass increase is by a binary merger. Thus, we have investigated these scenarios thoroughly. The obtained findings are that rotating single star models do not satisfy all the observational constraints and that the enhancement of envelope mass alone does not explain observations. Here, we consider a slow merger scenario in which both the He abundance and the envelope mass enhancements are expected to occur. We indeed show that most observational constraints such as the red-to-blue evolution, lifetime, total mass, position in the HR diagram at collapse, and the chemical anomalies are well reproduced by the merger model of 14 and 9 M ⊙ stars. We also discuss the effects of the added envelope spin in the merger scenarios.

Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single-star and Binary Merger Progenitor Models for SN 1987A

“…As discussed in Sections 4.2 and 4.3, among the investigated models in this paper, there is no explosion model with the BSG model n16.3 that satisfies the two observational constraints on the mass of high velocity 56 Ni simultaneously. On the other hand, with the BSG model b18.3 (binary merger model: Urushibata et al 2018) and two other RSG models s18.0 and s19.8 (Woosley et al 2002;Sukhbold et al 2016), we found several explosion models that satisfy the constraints. Thus, important questions are which properties of the pre-supernova models are essential to the matter mixing and why the properties have an advantage in the matter mixing.…”

“…Thus, the BSG progenitor models based on the single star evolution have both pros and cons. On the other hand, the binary merger model b18.3 (Urushibata et al 2018), which satisfies all observational constraints including the luminosity of Sk −69 • 202, has a smaller helium core mass (q value) than those of models based on the single star evolution that satisfy the luminosity of Sk −69 • 202, which may reflect the nature of merging processes, the penetration of the secondary into the envelope of the primary and the dredge up of the primary's core material into the envelope. Actually, the recent other binary merger models (Menon & Heger 2017) that satisfy the observational constraints all have a small helium core mass of ∼ 3-4 M (q ∼ 0.1-0.2) (see Table 4 in Menon & Heger 2017).…”

“…Later, Morris & Podsiadlowski (2007, 2009) successfully reproduced the formation of a triple ring structure very similar to the observed one based on 3D SPH simulations. Recently, progenitor models for SN 1987A based on the binary merger scenario have been developed by two independent groups (Menon & Heger 2017;Urushibata et al 2018). They has successfully found appropriate models that satisfy all the observational features of Sk −69 • 202 mentioned above.…”

“…They has successfully found appropriate models that satisfy all the observational features of Sk −69 • 202 mentioned above. Compared with Menon & Heger (2017), Urushibata et al (2018) included the effects of the spin-up of the envelope due to the angular momentum transfer from the orbit. Additionally, recent light curve modeling for SN 1987A (Menon et al 2019) based on the binary merger models (Menon & Heger 2017) have shown that the models better fit to the observed optical light curves than single star models.…”

“…In order to accomplish this, we perform 3D hydrodynamical simulations of core-collapse supernova explosions with four pre-supernova models, two are BSG models and the other two are RSG models. It is noted that a recent binary merger BSG model (Urushibata et al 2018) is adopted for the study of the matter mixing for the first time. First, we perform many lower resolution simulations to explore a wide range of parameters related to the asphericities of the explosion and the progenitor dependence.…”