JWST and HST observations of the host galaxy and supernova, SN 2024aihh in EP240801a at z=1.67

TL;DR

This paper reports JWST and HST observations of a distant gamma-ray burst-associated supernova at z=1.67, demonstrating the capability to study such events at high redshift and revealing properties similar to local counterparts.

Contribution

It presents the first spectroscopic identification of a GRB-SN at z=1.67 using JWST and HST, extending the observable redshift range for these phenomena.

Findings

The supernova is similar in luminosity and evolution to SN 1998bw.

The host galaxy has complex morphology with low surface brightness.

Little evolution in SN properties from local examples despite high redshift.

Abstract

We present James Webb Space Telescope (JWST) and Hubble Space Telescope (HST) observations of the counterpart of EP240801a, at z=1.67, the first fast X-ray transient (FXT) identified as an X-ray flash (XRF) by the Einstein Probe (EP) and Fermi-GBM. Our observations reveal strong photometric and spectroscopic evidence for an associated broad-lined Type Ic supernova (SN) SN 2024aihh, the most distant spectroscopically identified gamma ray-burst (GRB)-SN to date. The SN exhibits similar luminosity and light curve evolution to the proto-type GRB-SN 1998bw with an absolute magnitude of the SN at $\sim$23 days rest-frame of $M_{F140W} \approx$-19 mag. The SN is located in a host galaxy with complex morphology at a large ($\sim$6 kpc) offset in a region of relatively low surface brightness. The region around the SN has a modest star formation rate and is dominated by an intermediate mass-weighted age (1.4$\pm$0.3 Gyr) population, despite the apparent presence of a young, massive broad-lined Type Ic SN progenitor. These observations demonstrate that observations with HST and JWST can greatly extend the redshift range over which the GRB/FXT-SN connection can be studied, including in relatively low luminosity, X-ray rich events. They demonstrate little apparent evolution in the SN properties from local examples despite EP240801a originating from an epoch 10 Gyr ago.