We conduct one-dimensional stellar evolution simulations in the mass range 13 − 20M⊙ to late core collapse times and find that an inner vigorous convective zone with large specific angular momentum fluctuations appears at the edge of the iron core during the collapse. The compression of this zone during the collapse increases the luminosity there and the convective velocities, such that the specific angular momentum fluctuations are of the order of $j_{\rm conv} \simeq 5 \times 10^{15} {~\rm cm}^2 {~\rm s}^{-1}$. If we consider that three-dimensional simulations show convective velocities that are three to four times larger than what the mixing length theory gives, and that the spiral standing accretion shock instability in the post-shock region of the stalled shock at a radius of $\simeq 100 {~\rm km}$ amplify perturbations, we conclude that the fluctuations that develop during core collapse are likely to lead to stochastic (intermittent) accretion disks around the newly born neutron star. In reaching this conclusion we also make two basic assumptions with uncertainties that we discuss. Such intermittent disks can launch jets that explode the star in the frame of the jittering jets explosion mechanism.

We conduct one dimensional (1D) stellar evolution simulations of non-rotating stars with initial masses in the range of 11 − 48M⊙ to the time of core collapse and, using a criterion on the specific angular momentum fluctuations in the inner convective zones, estimate the masses of the neutron star (NS) remnants according to the jittering jets explosion mechanism. From the 1D simulations we find that several convective zones with specific angular momentum fluctuations of $j_{\rm {conv}} \gtrsim 2.5 \times 10^{15} {~\rm cm}^2 {~\rm s}^{-1}$ develop near the edge of the iron core in all models. For this condition for explosion we find the NS remnant masses to be in the range of 1.3 − 1.8M⊙, while if we require twice as large values, i.e., $j_{\rm {conv}} \gtrsim 5 \times 10^{15} {~\rm cm}^2 {~\rm s}^{-1}$, we find the NS remnant masses to be in the range of 1.4 − 2.8M⊙ (the upper values here might form black holes). Note that in general the formation of black holes in the jittering jets explosion mechanism requires a rapidly rotating pre-collapse core, while we simulate non-rotating stars.

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We simulate the evolution of eccentric binary systems in the frame of the grazing envelope evolution (GEE) channel for the formation of Type IIb supernovae (SNe IIb), and find that extra mass removal by jets increases the parameter space for the formation of SNe IIb in this channel. To explore the role of eccentricity and the extra mass removal by jets we use the stellar evolutionary code MESA binary. The initial primary and secondary masses are M1, i = 15M⊙ and M2, i = 2.5M⊙. We examine initial semi-major axes of 600 − 1000R⊙, and eccentricities of e = 0 − 0.9. Both Roche lobe overflow (RLOF) and mass removal by jets, followed by a wind, leave a hydrogen mass in the exploding star of MH, f ≈ 0.05M⊙, compatible with a SN IIb progenitor. When the initial orbit is not circular the final orbit might have a very high eccentricity. In many cases, with and without the extra mass removal by jets, the system can enter a common envelope evolution (CEE) phase, and then gets out from it. For some ranges of eccentricities the jets are more efficient in preventing he CEE. Despite the large uncertainties, extra mass removal by jets substantially increases the likelihood of the system to get out from a CEE. This strengthens earlier conclusions for circular orbits. In some cases RLOF alone, without mass removal by jets, can form SN IIb progenitors. We estimate that the extra mass removal by jets in the GEE channel increases the number of progenitors relative to that by RLOF alone by about a factor of two.

We examine the binding energies of massive stripped-envelope core collapse supernova (SECCSN) progenitors with the stellar evolution code mesa, and find that the jittering jets explosion mechanism is preferred for explosions where carbon-oxygen cores with masses of $\gtrsim 20 \, \mathrm{M}_\odot$ collapse to leave a neutron star (NS) remnant. We calculate the binding energy at core collapse under the assumption that the remnant is a NS. Namely, stellar gas above mass coordinate of ≃ 1.5 − 2.5 M⊙ is ejected in the explosion. We find that the typical binding energy of the ejecta of stripped-envelope progenitors with carbon-oxygen core masses of $M_{\rm CO} \gtrsim 20 \, \mathrm{M}_\odot$ is $E_{\rm bind} \gtrsim 2 \times 10^{51} {~\rm erg}$. We claim that jets are most likely to explode such cores as jet-driven explosion mechanisms can supply high energies to the explosion. We apply our results to SN 2020qlb, which is a SECCSN with a claimed core mass of ≃ 30 − 50 M⊙, and conclude that the jittering jets explosion mechanism best accounts for such an explosion that leaves a NS.

We examine the binding energy of massive stripped-envelope core collapse supernova (SECCSN) progenitors with the stellar evolution code mesa, and find that only the jittering jets explosion mechanism can account for explosions where carbon-oxygen cores with masses of 20M collapse to leave a neutron star (NS) remnant. We calculate the binding energy at core collapse under the assumption that the remnant is a NS. Namely, stellar gas above mass coordinate of 1.5 − 2.5M is ejected in the explosion. We find that the typical binding energy of the ejecta of stripped-envelope progenitors with carbon-oxygen core masses of M CO 20M is E bind 2 × 10 51 erg. Since only jet-driven explosion mechanisms can supply such high energies, we conclude that jets must explode such cores. We apply our results to SN 2020qlb, which is a SECCSN with a claimed core mass of 30 − 50M , and conclude that the jittering jets explosion mechanism best account for such an explosion that leaves a NS.

This article discusses the torsion problem of a continuous cylindrical specimen used to construct a hardening curve. A brief review of the methods for processing the results of the method of torsion of a cylindrical specimen is given. The possibility of using the inverse method to determine the material model in the case of the torsion of the continuous cylindrical specimen made of steel 20H is shown. By means of QFORM 9.0 software package virtual experiment connected with torsion of a cylindrical specimen is carried out. As a result of this research, the rheological model of steel 20His determined with a high degree of accuracy. The stress-strain state of the material was analyzed during the torsion of the specimen by means of the QFORM. The results of the virtual experiment are compared with the full-scale test.Anexceptionally good match of the results was obtained. The inverse method showed its efficiency and made it possibleto determine a rheological model of the material. The model accurately describes the experimental data. The resulting material model (for steel 20H) is valid in the following range of parameters: deformation temperature of 20°C, deformation rate of 0.5 s−1, the strain range of 0 to 2.5.