The Progenitor of the Type II-Plateau SN 2025pht in NGC 1637: The Dustiest, Most Luminous Red Supergiant So Far?

TL;DR

This study characterizes the progenitor of SN 2025pht, a heavily dust-enshrouded, luminous red supergiant observed shortly before explosion, using unprecedented multi-epoch data from HST and JWST.

Contribution

It provides the first near-complete characterization of a supernova progenitor shortly before explosion, highlighting the importance of JWST data for such studies.

Findings

Progenitor star was heavily obscured by dust with A_V~1.7 mag.

Star's bolometric luminosity is log(L_bol/L_Sun)=5.08.

Candidate may be the most luminous RSG progenitor identified.

Abstract

We provide a characterization of the red supergiant (RSG) progenitor candidate for the nearby Type II-plateau supernova (SN) 2025pht in NGC 1637. The star was first detectable in 2001 by the Hubble Space Telescope (HST) and then again in a dozen bands by the James Webb Space Telescope (JWST) in 2024. This "quasi-snapshot" of the star's nature almost immediately prior to explosion is unprecedented. The RSG varied in brightness, and we posit that it could have been a pulsating variable, possibly with a long period of ~660 days. The largest uncertainty is the host-galaxy distance, which we establish to be 10.73+/-1.76 Mpc. The star was also heavily extinguished by interstellar dust internal to the host, with visual extinction A_V(host)~1.7 mag (total A_V(tot)~1.8 mag). Dust radiative-transfer modeling reveals the star's circumstellar medium to be quite dusty and silicate-rich, yielding a bolometric luminosity log(L_bol/L_Sun)=5.08+/-0.16 and a cool effective temperature T_eff=2100--2500 K. The available HST optical data had no bearing on the shape of the candidate's observed spectral energy distribution -- for the first time, without the archival JWST observations we would not have been able to detect and characterize the candidate at all. The SN 2025pht progenitor candidate, although quite similar to that of SN 2023ixf, may be the most luminous candidate identified to date.