SN 2026ahvu in NGC 1433 May Be a Prompt Type Ia Supernova with a Delay Time Under 100 Myr

Abstract

SN 2026ahvu is a Type Ia supernova (SN) that occurred in the nearby galaxy NGC 1433. Using archival Hubble and JWST imaging from the PHANGS survey, we show that the SN lies within 0.19${}^{\prime \prime }$ and 0.26${}^{\prime \prime }$ of two UV-bright star clusters. This $0.19/0.26^{\prime \prime }$ separation corresponds to $8/11$ pc ($17/24$ pc) at the reported distances of $9.1$ and $18.9$ Mpc, respectively. The probability of finding an unrelated Type Ia SN this close to a cataloged star cluster by chance is only $\sim$0.4 %. Thus, SN 2026ahvu is likely the first Type Ia SN that can be associated with relatively young star clusters in a nearby galaxy. From spectral energy distribution fitting using HST+JWST (or HST-only) data, we find that the clusters have age estimates of $37_{-5}^{+3}$ ($57_{-9}^{+14}$) Myr and $95_{-13}^{+15}$ ($88_{-12}^{+14}$) Myr. Association with either cluster would mean that SN 2026ahvu should be considered a prompt SN Ia and provide one of the most concrete measurements to date of a prompt Ia delay time. The median age of the younger star cluster is close to the minimum possible delay time for SN Ia progenitors. If the SN is indeed associated with the younger cluster, it would imply that Type Ia SNe can occur almost immediately after white dwarf formation. If the SN is associated with the older cluster, this discovery still presents the first example of a prompt Type Ia SN with delay time under 100 Myr.

arXiv comment10 pages, 2 figures, 1 table. Submitted to ApJL