Aadya Agrawal, Justin Pierel, Gautham Narayan, Brenda Frye, J. M. Diego, Nikhil Garuda, Matthew Grayling, Anton M. Koekemoer, Kaisey S. Mandel, M. Pascale, David Vizgan, Rogier A. Windhorst
Abstract Supernova (SN) H0pe is a multiply-imaged Type Ia supernova (SN Ia) and the second lensed SN to yield a measurement of the Hubble constant by the time-delay cosmography method, finding H 0 = 75 . 4 − 5.5 + 8.1 km s − 1 Mpc − 1 . We investigate the seven lens modeling approaches used to derive H 0 , assessing their agreement with ΛCDM constraints from SN Ia surveys through a purely observational comparison. We test each lens model by combining its predicted magnifications with the observed time delays to reconstruct the intrinsic SN Ia luminosity and corresponding distance modulus. While photometrically derived magnifications yield distance moduli in line with ΛCDM expectations, our comparison reveals that lens model predictions, even the most precise ones, consistently overestimate the magnification, with an offset > 1 mag. This known bias, already appreciated by modeling teams, is independently confirmed through our analysis and highlights the value of lensed SNe as a tool to test model accuracy. If unaccounted for, such magnification biases can propagate into uncertainties in derived cosmological parameters, including H 0 , a critical challenge for precision cosmology using strongly lensed transients.