paper

Shock cooling of a red-supergiant supernova at redshift 3 in lensed images

arXiv:2306.12985 · doi:10.1038/s41586-022-05252-5

Abstract

The core-collapse supernova of a massive star rapidly brightens when a shock, produced following the collapse of its core, reaches the stellar surface. As the shock-heated star subsequently expands and cools, its early-time light curve should have a simple dependence on the progenitor's size and therefore final evolutionary state. Measurements of the progenitor's radius from early light curves exist for only a small sample of nearby supernovae, and almost all lack constraining ultraviolet observations within a day of explosion. The several-day time delays and magnifying ability of galaxy-scale gravitational lenses, however, should provide a powerful tool for measuring the early light curves of distant supernovae, and thereby studying massive stellar populations at high redshift. Here we analyse individual rest-frame ultraviolet-through-optical exposures taken with the Hubble Space Telescope that simultaneously capture, in three separate gravitationally lensed images, the early phases of a supernova at redshift beginning within hr of explosion. The supernova, seen at a lookback time of billion years, is strongly lensed by an early-type galaxy in the Abell 370 cluster. We constrain the pre-explosion radius to be solar radii, consistent with a red supergiant. Highly confined and massive circumstellar material at the same radius can also reproduce the light curve, but is unlikely since no similar low-redshift examples are known.

69 pages, 12 figures/tables (4 main text, 8 extended data). Published in Nature

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