Discovery of SN 2025wny: a Strongly Gravitationally Lensed Superluminous Supernova at z = 2.01

TL;DR

The paper reports the discovery and spectroscopic confirmation of the first gravitationally lensed Type I superluminous supernova at redshift 2.01, demonstrating the potential of ground-based observations for studying distant supernovae and cosmology.

Contribution

This is the first detection and detailed analysis of a gravitationally lensed SLSN-I at such a high redshift, expanding observational capabilities.

Findings

Four images of the supernova were resolved with ~1.7" separation.

Magnification factor of 20 to 50 for the brightest image.

Ground-based facilities can observe high-redshift lensed supernovae.

Abstract

We present the discovery of SN 2025wny (ZTF25abnjznp/GOTO25gtq) and spectroscopic classification of this event as the first gravitationally lensed Type I superluminous supernovae (SLSN-I). Deep ground-based follow-up observations resolves four images of the supernova with ~1.7" angular separation from the main lens galaxy, each coincident with the lensed images of a background galaxy seen in archival imaging of the field. Spectroscopy of the brightest point image shows narrow features matching absorption lines at a redshift of z = 2.011 and broad features matching those seen in superluminous SNe with Far-UV coverage. We infer a magnification factor of 20 to 50 for the brightest image in the system, based on photometric and spectroscopic comparisons to other SLSNe-I. SN 2025wny demonstrates that gravitationally-lensed SNe are in reach of ground-based facilities out to redshifts far higher than what has been previously assumed, and provide a unique window into studying distant supernovae, internal properties of dwarf galaxies, as well as for time-delay cosmography.