Follow-up of SN 2025wny V: Lens Modelling and Cosmography of a Strongly Lensed Superluminous Supernova at z = 2.015 using Space Data

We present a lensing and cosmographic analysis of the strongly lensed Type I superluminous supernova SN 2025wny at redshift z=2.015, multiply imaged by two foreground galaxies at z=0.376. Using imaging obtained with the Hubble Space Telescope and the James Webb Space Telescope, we model the lens system with two elliptical power-law mass distributions and an external shear component. In addition to the supernova image positions, the modelling incorporates the surface-brightness distribution of the lensed host galaxy. The inferred Einstein radii are θ E,1 1.6 " and θ E,2 0.7 - 0.8 ", with broadly consistent results across all filters. After accounting for microlensing by stars in the lens galaxies, the posterior distribution spans total magnifications of approximately μ tot about 5 -- 50, with flux ratios of the multiple images consistent with observations. Combining the lens models with spectroscopically and photomerically measured time delays yields a filter-marginalized constraint of H 0 = 66.7+7.6-6.3; km,s-1,Mpc-1, for a fiducial model with isothermal mass profiles. Allowing the density slopes of the lens galaxies to vary over a broad range results in H 0 = 70.8+8.2-6.1; km,s-1,Mpc-1. These values are conditional on the adopted parameterization of the lens mass distribution, the assumed priors on the density slopes, and possible additional lensing contributions from the surrounding large-scale environment. We find that incorporating the currently available stellar kinematic measurements has only a modest effect on the inferred value of H 0. Future measurements of the lens-galaxy kinematics and a detailed characterization of the lens environment will further strengthen the utility of SN 2025wny as a cosmological probe.