[Cosmology seminar] A Glimpse at a New Cosmological Probe in the Era of LSST: Time Delays of Gravitationally Lensed Supernovae using Gaussian Processes

Gravitationally lensed supernovae (glSNe) are powerful local probes of the Hubble parameter (H0), as they are independent of the distance ladder and insensitive to the assumed cosmological model. Despite their rarity, the Rubin Observatory’s Legacy Survey of Space and Time (LSST) will increase the discovery rate of glSNe by an order of magnitude. In this talk, we present a comprehensive analysis of follow-up strategies for glSNe discovered by LSST based on how well time delays are estimated from the Glimpse model for time-delay estimation (Hayes+25b), built upon the GausSN framework (Hayes+24). Glimpse simultaneously models data in which the multiple images of the glSN are resolved and in which they are unresolved for the first time to achieve robust time-delay estimates. The model also accounts for chromatic microlensing, host galaxy dust extinction, and differential dust extinction in the lens galaxy in the statistical error budget. We apply this model to simulated glSN Ia systems with realistic LSST data and varying amounts of space- and ground-based follow-up. Whereas without follow-up, the time delay of an unresolved system on the dimmest end of detectability by LSST, having peak i-band magnitudes of 22-24 mag, can only be constrained to of order a week, the time delays are measured to as low as 0.7 day uncertainty with 6-8 epochs of resolved space-based observations. For systems of similar brightness that are resolved by ground-based facilities, time delays are consistently constrained to 0.5-0.8 day precision with 6 epochs of space-based observations or 8 epochs of deep ground-based observations. This work improves on previous time-delay estimation methods and demonstrates that glSNe time delays of ~10-20 days can be measured to sufficient precision for competitive H0 estimates in the Rubin-LSST era.