Kavli Affiliate: Kaisey Mandel
| Summary:
Supernova 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 $H_0 = 75.4^+8.1_-5.5 textkm s^-1 textMpc^-1$ (Pascale et. al 2025). We investigate the seven lens modeling approaches used to derive $H_0$, assessing their agreement with $ΛtextCDM$ constraints from SN~Ia surveys through a purely observational comparison. textbfWe 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 $ΛtextCDM$ expectations, our comparison reveals that lens model predictions, even the most precise ones, textbfconsistently 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.
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