We build a toy model where the central object, i.e., a newly born neutron star or a black hole, launches jets at late times and show that these jets might account for peaks in the light curve of some peculiar core collapse supernovae (CCSNe) when the jets interact with the CCSN ejecta. We assume that the central object accretes fall back material and launches two short-lived opposite jets weeks to months after the explosion. We model each jet-ejecta interaction as a spherically symmetric 'mini explosion' that takes place inside the ejecta. In our toy model late jets form stronger emission peaks than early jets. Late jets with a kinetic energy of only about one percent of the kinetic energy of the CCSN itself might form strong emission peaks. We apply our toy model to the brightest peak of the enigmatic CCSN iPTF14hls that has several extra peaks in its light curve. We can fit this emission peak with our toy model when we take the kinetic energy of the jets to be about one percent of the CCSN energy, and the shocked ejecta mass to be about one percent of the ejecta mass.

We apply the jet-powered ILOT scenario to two recently studied intermediate luminosity optical transients (ILOTs), and find the relevant shell mass and jets’ energy that might account for the outbursts of these ILOTs. In the jet-powered ILOT scenario, an accretion disk around one of the stars of a binary system launches jets. The interaction of the jets with a previously ejected slow shell converts kinetic energy to thermal energy, part of which is radiated away. We apply two models of the jet-powered ILOT scenario. In the spherical shell model, the jets accelerate a spherical shell, while in the cocoon toy model the jets penetrate into the shell and inflate hot bubbles, the cocoons. We find consistent results. For the ILOT (ILRT: intermediate luminosity red transient) SNhunt120 we find the shell mass and jets’ energy to be M s ≃ 0.5 − 1 M ⊙ and E 2j ≃ 5 × 1047 erg, respectively. The jets’ half opening angle is αj ≃ 30° − 60°. For the second peak of the ILOT (luminous red nova) AT 2014ej we find these quantities to be M s ≃ 1 − 2 M ⊙ and E 2j ≃ 1.5 × 1048 erg, with αj ≃ 20° − 30°. The models cannot tell whether these ILOTs were powered by a stellar merger that leaves one star, or by mass transfer where both stars survived. In both cases the masses of the shells and energies of the jets suggest that the binary progenitor system was massive, with a combined mass of M 1 + M 2 ≳ 10 M ⊙.

We build three simple bipolar ejecta models for core-collapse supernovae (CCSNe), as expected when the explosion is driven by strong jets, and show that for an observer located in the equatorial plane of the ejecta, the light curve has a rapid luminosity decline, and even an abrupt drop. In calculating the geometrically modified photosphere we assume that the ejecta has an axisymmetrical structure composed of an equatorial ejecta and faster polar ejecta, and has a uniform effective temperature. At early times the photosphere in the polar ejecta grows faster than the equatorial one, leading to higher luminosity relative to a spherical explosion. The origin of the extra radiated energy is the jets. At later times the optical depth decreases faster in the polar ejecta, and the polar photosphere becomes hidden behind the equatorial ejecta for an observer in the equatorial plane, leading to a rapid luminosity decline. For a model where the jets inflate two low-density polar bubbles, the luminosity decline might be abrupt. This model enables us to fit the abrupt decline in the light curve of SN 2018don.

We use the two-components bipolar toy model of core collapse supernova (CCSN) ejecta to fit the rapid decline from maximum luminosity in the light curve of the type IIb CCSN SN 2018gk (ASASSN-18am). In this toy model we use a template light curve from a different CCSN that is similar to SN 2018gk, but that has no rapid drop in its light curve. The bipolar morphology that we model with a polar ejecta and an equatorial ejecta increases the maximum luminosity and causes a steeper decline for an equatorial observer, relative to a similar spherical explosion. The total energy and mass of our toy model for SN 2018gk are E SN = 5 × 10 51 erg and M SN = 2.7 M ⊙ . This explosion energy is more than what a neutrino driven explosion mechanism can supply, implying that jets exploded SN 2018gk. These energetic jets likely shaped the ejecta to a bipolar morphology, as our toy model requires. We crudely estimate that f ≈ 2%–5% of all CCSNe show this behavior, most being hydrogen deficient (stripped-envelope) CCSNe, as we observe them from the equatorial plane. We estimate the overall fraction of CCSNe that have a pronounced bipolar morphology to be f bip ≈ 5%–15% of all CCSNe.

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