JWST Photometric Time-delay and Magnification Measurements for the Triply Imaged Type Ia “SN H0pe” at z = 1.78

Supernova (SN) SN H0pe is a gravitationally lensed, triply imaged, Type Ia SN (SN Ia) discovered in James Webb Space Telescope imaging of the PLCK G165.7+67.0 cluster of galaxies. Well-observed multiply imaged SNe provide a rare opportunity to constrain the Hubble constant ( H 0 ), by measuring the relative time delay between the images and modeling the foreground mass distribution. SN H0pe is located at z = 1.783 and is the first SN Ia with sufficient light-curve sampling and long enough time delays for an H 0 inference. Here we present photometric time-delay measurements and SN properties of SN H0pe. Using JWST/NIRCam photometry, we measure time delays of Δ t ab = − 116.6 − 9.3 + 10.8 observer-frame days and Δ t cb = − 48.6 − 4.0 + 3.6 observer-frame days relative to the last image to arrive (image 2b; all uncertainties are 1 σ ), which corresponds to a ∼5.6% uncertainty contribution for H 0 assuming 70 km s −1 Mpc −1 . We also constrain the absolute magnification of each image to μ a = 4.3 − 1.8 + 1.6 , μ b = 7.6 − 2.6 + 3.6 , μ c = 6.4 − 1.5 + 1.6 by comparing the observed peak near-IR magnitude of SN H0pe to the nonlensed population of SNe Ia.