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Energetics of the ultra-high-energy cosmic rays (UHECRs) generated in the universe is crucial for pinning down their candidate sources. In this talk, I will introduce our recent works about UHECR energy generation rate density for different species of nuclei at the injection, considering intermediate and heavy nuclei as well as protons.
Our results imply that a large amount of nuclei have to be loaded in the sources whatever the spectral index is, which is theoretically challenging. One possibility is the massive stellar origin of heavy nuclei, and low-luminosity GRBs and engine-driven supernovae provide a natural solution. Another possibility is the reacceleration of galactic cosmic rays by jets or outflows. Finally, I will discuss the newly designed and developed experiments, such as the next-generation AugerPrime experiment, the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) mission, and the Giant Radio Array for Neutrino Detection (GRAND), the systematic error will then be reduced in a more extended energy scale. Together with other observables such as anisotropy in arrival directions of UHECRs, this will help constrain source models and have implications for the origins of UHECRs.
Bing Theodore Zhang obtained the doctoral degree in astrophysics in 2019 at Peking University, and he was a visiting scholar at the Pennsylvania State University during 2016-2017 supported by China Scholarships Council Fellowship. After his Ph.D., Bing becomes a postdoctoral research scholar in the department of physics and the Institute for Gravitation \& the Cosmos (IGC) at the Pennsylvania State University working with Prof. Kohta Murase and Prof. Miguel Mostafa. Bing's interests lie at the intersection of astroparticle physics and high-energy astrophysics. Bing is currently working on developing time-dependent numerical code for the production and propagation of ultra-high-energy cosmic rays, neutrinos, and gamma-rays for various astrophysical environments. Bing is also a member of Giant Radio Array for Neutrino Detection (GRAND) Collaboration, where he works on the design of a conventional ground array for hybrid detection of the extensive air showers.