Impact of effective matter mixing on molecule formation in the ejecta of SN 1987A based on 3D hydrodynamical models

Masaomi Ono^1,2,3*, Takaya Nozawa⁴, Shigehiro Nagataki^2,3,5, Alexandra Kozyreva⁶, Salvatore Orlando⁷, Marco Miceli⁸, Ke-Jung Chen¹

¹Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
²Astrophysical Big Bang Laboratory (ABBL), RIKEN Cluster for Pioneering Research, Saitama, Japan
³RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS), Saitama, Japan
⁴Division of Theoretical Astronomy, National Astronomical Observatory of Japan (NAOJ), Tokyo, Japan
⁵Astrophysical Big Bang Group (ABBG), Okinawa Institute of Science and Technology Graduate University (OIST), Okinawa, Japan
⁶Heidelberger Institut für Theoretische Studien, Heidelberg, Germany
⁷INAF-Osservatorio Astronomico di Palermo, Palermo, Italy
⁸Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Palermo, Italy

* Presenter:Masaomi Ono, email:masaomi@asiaa.sinica.edu.tw

More than 30 years after the discovery of SN 1987A, it has entered a phase of a young supernova remnant. The observations of the spatially resolved inner ejecta have provided a unique opportunity to investigate the early evolution of core-collapse supernovae (CCSNe) to their supernova remnants. Recent breakthrough observations by ALMA (Abellán et al. 2017) have revealed three-dimensional (3D) distributions of carbon and silicon monoxides (CO and SiO) in the ejecta of SN 1987A and those are rather non-spherical and lumpy. How molecules are formed in CCSNe has, however, still been unclear. Additionally, very recent JWST observations (Larsson et al. 2023) have shown a dipole-like iron distribution in the ejecta of SN 1987A. Together with the ALMA observations, it may provide insights into the unknown explosion mechanism by comparing it with theories. Our previous study (Ono et al. 2020) on the matter mixing in SN 1987A based on 3D hydrodynamical models has revealed that an asymmetric bipolar-like explosion with a binary merger progenitor model better explains the observed iron line profiles ([Fe II]: Haas et al. 1990), which is known as one of the evidence of matter mixing in SN 1987A, compared with models with a single-star progenitor model. The distribution of the seed atoms affected by the matter mixing before the molecule formation may play a role in the formation of molecules in the ejecta.

To investigate the impact of matter mixing on the formation of molecules in the ejecta of SN 1987A, we perform time-dependent rate equation calculations for chemical reactions (Ono et al. 2023, submitted to ApJS: arXiv:2305.02550) with one-dimensional ejecta profiles based on the 3D hydrodynamical models of SN 1987A. It is found that the matter mixing could play a non-negligible role in the formation and destruction of molecules, in particular CO and SiO, through several reaction sequences induced by the decay of radioactive ⁵⁶Ni (⁵⁶Co). Some of the results and how ⁵⁶Ni affects the formation and destruction of molecules are presented.

Keywords: Core-collapse supernovae, 3D hydrodynamics, Matter mixing, Molecule formation, SN 1987A