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

Agnes P. C. van Hoof; Andrew J. Levan; Peter G. Jonker; Morgan Fraser; Luca Izzo; Andrew S. Fruchter; Joyce N. D. van Dalen; Nial R. Tanvir; Jens Hjorth; Antonio Martin-Carrillo; Nikhil Sarin; Laura C. Cotter; Jonathan A. Quirola-Vásquez; Maria E. Ravasio; Javi Sánchez-Sierras; Manuel A. P. Torres; Shuai-Qing Jiang; Dong Xu

Paper

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

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

23 days rest-frame of

-19 mag. The SN is located in a host galaxy with complex morphology at a large (

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

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.