Primary and secondary source of energy in the superluminous supernova 2018ibb

¹ Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
² GSI Helmholtzzentrum für Schwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany
³ National Research Center, Kurchatov Institute, pl. Kurchatova 1, Moscow 123182, Russia
⁴ Lebedev Physical Institute, Russian Academy of Sciences, 53 Leninsky Avenue, Moscow 119991, Russia
⁵ Space Research Institute (IKI), Profsoyuznaya 84/32, Moscow 117997, Russia
⁶ M.V. Lomonosov Moscow State University, Sternberg Astronomical Institute, 119234 Moscow, Russia
⁷ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany

Received: 9 March 2024
Accepted: 30 May 2024

Abstract

We examined a possible pair-instability origin for the superluminous supernova 2018ibb. As the base model, we used a non-rotating stellar model with an initial mass of 250 M_⊙ at about 1/15 solar metallicity. We considered three versions of the model as input for radiative transfer simulations done with the STELLA and ARTIS codes: with 25 M_⊙ of ⁵⁶Ni, with 34 M_⊙ of ⁵⁶Ni, and a chemically mixed case with 34 M_⊙ of ⁵⁶Ni. We present light curves and spectra in comparison to the observed data of SN 2018ibb, and conclude that the pair-instability supernova model with 34 M_⊙ of ⁵⁶Ni explains the broadband light curves reasonably well between −100 and 250 days around the peak. Our synthetic spectra have many similarities with the observed spectra. The luminosity excess in the light curves and the blue-flux excess in the spectra can be explained by an additional energy source, which may be an interaction of the supernova ejecta with circumstellar matter. We discuss possible mechanisms that could have caused the circumstellar matter to be ejected in the decades before the pair-instability explosion.