Massive stars are among the most influential components of the Universe. They enrich their host galaxies with heavy elements, and emit large amounts of energy through their radiation and winds. They end their lives with the collapse of their iron cores, which may result in energetic stellar explosions. I will present possible channels of massive star evolution that can produce explosions which are hydrogen- and helium-deficient in different metallicity environments.
Properties of transients in the local universe can be studied through massive helium stars, which are expected to emerge from stars whose hydrogen-rich envelope is stripped off by a binary companion. I will discuss stellar evolution models of helium stars, the expected properties of the transients they produce, and show them to be representative of hydrogen-deficient supernovae of Types Ib and Ic.
In low metallicity environments, such transients might originate from fast-rotating massive stars. I will discuss stellar evolution models where rotation induces strong mixing in the whole stellar interior, and can lead to almost complete burning of hydrogen and helium. During their final years of evolution, the increasing neutrino emission can lead to a spin-up, which translates into rotationally induced mass loss that may affect their final explosion. Due to their metal-rich composition and high angular momentum content, these models may correspond to progenitors of both superluminous supernovae and gamma-ray bursts. I will show that they can reproduce the observed properties of most superluminous supernovae in the context of the magnetar model.