MIfA Colloquium - Lei Hu (Carnegie Mellon)

Title: From Image Differencing to Transient Discovery in Time-Domain Surveys

Abstract: Difference Image Analysis (DIA) is a core technique enabling the discovery and characterization of astrophysical transients in time-domain surveys. DIA serves to homogenize the ubiquitous variations in point-spread function (PSF), photometric scaling, and sky background across epochs in images obtained with both ground- and space-based telescopes. In this talk, I will review the underlying principles of DIA and summarize commonly used approaches in the time-domain community, with particular emphasis on our SFFT algorithm. I will present SFFT-based pipelines developed for ongoing ground-based DECam surveys (DESIRT and GW-MMADS), JWST time-domain programs (JCAST and NEXUS), and the Roman Supernova Cosmology project. I will then briefly demonstrate their applications to gravitational-wave follow-up of the candidate neutron star–black hole merger S250206dm, as well as ongoing searches for high-redshift transients with JWST.