A New FU Orionis Accretion Outburst in the W5 HII Region

TL;DR

This paper reports the detection and analysis of a recent FU Orionis-type outburst in the W5 HII region, providing multi-wavelength lightcurves and spectroscopic confirmation of the outburst's nature.

Contribution

It presents the first observation of a new FU Orionis outburst in W5, with detailed lightcurves and spectroscopic data confirming its classification.

Findings

Outburst amplitude of approximately 4 magnitudes in r-band

Outburst duration of about 75 days

Spectroscopic features consistent with FU Ori objects

Abstract

We announce a recently detected outburst that is currently only a few months old, and probably of FU Orionis type. The progenitor to the outburst was an emission-line, flat-spectrum SED young stellar object located in the W5 region, though somewhat outside the main star formation action. We present optical, near-infrared, and mid-infrared lightcurves that illustrate the quiescent state of [KAG2008] 13656 and its subsequent$\Delta r \approx -4$ mag and $\Delta J\approx -3$ mag outburst over $\sim$75 days in late-2025. Follow-up optical and near-infrared spectroscopy confirms the expected features from an FU Ori disk and outflow.