JWST reveals a luminous infrared source at the position of the failed supernova candidate N6946-BH1

TL;DR

JWST observations of N6946-BH1 reveal a complex, blended infrared source with luminosity and spectral features that challenge the failed supernova interpretation, suggesting possible alternative explanations like a stellar merger.

Contribution

This study provides the first late-time JWST data showing the spectral energy distribution of N6946-BH1, revealing multiple sources and IR features that complicate its classification as a failed supernova.

Findings

All previous observations are a blend of at least 3 sources.

IR flux has brightened compared to the progenitor model.

IR spectral features are consistent with PAH emission from dust illuminated by UV radiation.

Abstract

N6946-BH1 is the first plausible candidate for a failed supernova (SN), a peculiar event in which a massive star disappears without the expected bright SN, accompanied by collapse into a black hole (BH). Following a luminous outburst in 2009, the source experienced a significant decline in optical brightness, while maintaining a persistent infrared (IR) presence. While it was proposed to be a potential failed SN, such behavior has been observed in SN impostor events in nearby galaxies. Here, we present late-time observations of BH1, taken 14 years after disappearance, using JWST's NIRCam and MIRI instruments to probe a never-before-observed region of the object's spectral energy distribution. We show for the first time that all previous observations of BH1 (pre- and post-disappearance) are actually a blend of at least 3 sources. In the near-IR, BH1 is notably fainter than the progenitor but retains similar brightness to its state in 2017. In the mid-IR, the flux appears to have brightened compared to the inferred fluxes from the best-fitting progenitor model. The total luminosity of the source is between 13 - 25% that of the progenitor. We also show that the IR SED appears consistent with PAH features that arise when dust is illuminated by near-ultraviolet radiation. At present, the interpretation of N6946-BH1 remains uncertain. The observations match expectations for a stellar merger, but theoretical ambiguity in the failed SN hypothesis makes it hard to dismiss.