Seminar of RPg Student:- The Nature of Transients in Abell 370
The study of gravitational lensing in galaxy clusters has been a keen topic in astronomy since its first discovery, where efforts were made to utilize lensing effects as a probe of the variety of galaxy cluster properties.
In recent years, the advanced imaging technologies allow astronomers to have high resolution images of galaxy clusters in multi-epochs, where numerous flux variation events – transients, are discovered in galaxy clusters. For instance, Ikarus(Kelly et al. 2017), Spock(Rodney et al. 2017), Warhol(Chen et al. 2019) and Earendel(Welch et al. 2022) events that feature the hypothesis of high redshift stars under high macro-magnification, were observed with temporary brightening due to microlensing. This opens up a new window in astronomy, where astronomers can actually glance at individual stars at high redshift. These stars are expected to have different properties and evolutionary paths in contrast to the stars formed in modern days, thus the transients in galaxy clusters become a precious tool in studying how stars in the past behave as well as the information they could carry about the evolution of the universe.
講者：LI Sung Kei(香港大學)
In this seminar, The speaker will present his work of investigating the nature of the transients in the galaxy cluster, Abell 370(A370). Among the 6 transients detected in A370 from the FLASHLIGHT project, he focuses on one of the transients which exhibited temporary brightening of an H-II region. The current hypothesis favours a Luminous Blue Variable Outburst with the energy budget of 4e40 erg s-1, but microlensing simulation tells that the possibility of it being a microlensing event might not be completely ruled out despite a very small likelihood (<1%).