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Although looking serene to human eyes, the night sky appears as a spectacular cosmic firework display. These fleeting phenomena, known as astronomical transients, reveal them across the whole electromagnetic spectrum. A large fraction of these transients are supernovae (SNe) or other exotic stellar explosions. Unraveling the intricacies of how these explosion phenomena emerge and identifying their celestial sources has become one of the focal points in modern time-domain astronomy. In this talk, I will talk about recent observational progress in understanding the final explosion of stars, including thermonuclear explosion of white dwarfs, core-collapse of massive stars, and the new emerging population of fast-evolving transients. I will discuss observations spanning from the initial moments shortly after the explosion to very late times. I will show that observations in different phases of the transients allow us to probe different aspects of the explosion phenomena. For example, the infant phase probes the ambient environment and nebular phase penetrates the innermost ejecta of the explosion.
Half of the talk will be devoted to a recent discovery of the stripped envelope SN 2022jli in which a 12.4-day periodicity has been found (https://ui.adsabs.harvard.edu/abs/2023arXiv231007784C/abstract). The observed properties of SN2022jli, including periodic undulations in the optical light curve, coherent Hα emission shifting, and evidence for a gamma- ray source, point to the explosion of a massive star in a binary system leaving behind a bound compact remnant. Mass accretion from the companion star onto the compact object powers the light curve of the supernova and generates the gamma-ray emission. SN 2022jli builds the direct link between a massive star explosion and the formation of a compact object. The discovery of SN 2022jli opens a new window to directly probe the final evolution of massive compact binaries, including accretion-powered systems and, eventually, the progenitors of gravitational wave sources.
Ping Chen is a Benoziyo fellow at the Weizmann Institute of Science. He graduated from the department of Astronomy of Peking University in 2021. He has broad interest in observational studies on cosmic explosions especially supernovae.