News and Events

Under gravitational lensing, dim individual stellar objects at high redshift are made possible to be detected temporarily upon an extra boost of brightness over a short period. These objects are known as lensed transients where their temporary increase in brightness comes from either extrinsic phenomena such as stellar microlensing, or the intrinsic variability of the lensed sources themselves.

In my thesis, I investigated the nature of transients that comprise lensed star clusters in the galaxy cluster Abell 370 as detected by the Flashlights project. In particular, I made use of one of these transients which is multiply lensed itself, as a case study to understand what might have caused all these transients – Is stellar microlensing capable of explaining all these detections? Or intrinsic stellar outbursts could explain some, if not all, of the transients?

To tackle the scientific question, I first constructed a lens model to serve as the basis for understanding the nature of these transients. With the lens model, various light curves generated for the experimented multiply-lensed star cluster did not rule out nor confirm any of the hypotheses, but implied that LBVs could be a possible explanation behind some of the detected transients; Based on my lens model, I designed a simulation to address the role of stellar microlensing in generating these lensed star cluster transients. The simulation predicts a detection rate of lensed star cluster transients that is consistent with the observation within 1σ uncertainty, indicating that stellar microlensing alone can explain all the detected lensed star cluster transients. Last but not least, this consistency allowed me to place constraints on the abundance of Primordial Blackholes in Dark Matter, down to ≲ 1% with 3σ confidence.