The TransPIre project seeks to understand the final fates of the most massive stars in the Universe. The evolution and end fate of such stars are important for many different areas of astrophysics, ranging from understanding the very first stars and galaxies, the formation of heavy elements and galaxy enrichment, the physics of supernova explosions, and the formation of compact objects like neutron stars and black holes.
Since the 1960s, it has been hypothesised that the most massive stars -- those whose helium cores exceed about 35 solar masses -- will evolve in a fundamentally different way than their less massive counterparts, because the core temperatures get high enough for spontaneous electron-positron production. This in turn momentarily softens the equation of state, removing pressure support in the stellar core and leads to an instability that can either give rise to a series of pulsations and mass ejections before the star ends in a core-collapse, or, in the most massive regime, lead to the runaway thermonuclear explosion of the entire stellar core, a so-called pair-instability supernova. In the latter case, there is no compact remnant left behind. With the discovery of black holes in the pair-instability mass range by gravitational wave experiments like LIGO/Virgo, as well as the focus on the first stars and galaxies with the successful launch of James Webb Space Telescope, it is crucial to understand this regime in stellar evolution in order to be able to interpret the results.
At the same time, new experiments in time-domain astronomy are coming online, such as the LSST project at the Vera Rubin Observatory in 2025. Its combination of area, depth and cadence gives unprecedented survey volumes allowing for the detection of rare events, and in particular, predictions from stellar evolution modeling tuned to explain the black hole population seen by LIGO/Virgo suggests that there should be pair-instability supernovae present in the LSST data stream. This project aims to exploit this opening of parameter space to search for transients related to the pair-instability phenomenon -- both full-blown pair-instability supernovae, and those resulting from pulsational pair-instability mass loss.
