SPICY 30021: An embedded bona fide FU Orionis star with a mid-infrared precursor

The unstable mass accretion process in young stellar objects often leads to observable outbursts. These episodic accretion bursts play a key role in the stellar mass assembly during the pre-main-sequence evolution. The outbursts with the highest amplitude and longest duration are commonly identified as FU Orionis stars (FUors). Only ∼50 FUor events were confirmed until recently. Most of these eruptive events occur in embedded protostars, which are difficult to monitor from optical surveys. We present photometric and spectroscopic observations of an eruptive young star (SPICY 30021) originally discovered from the mid-infrared time series. We constructed the spectral energy distribution and physically characterised the eruptive nature of SPICY 30021. NEOWISE We gathered multi-wavelength photometric time series from , VVV, and the recently established VVV-RENEW surveys. We also conducted photometric and spectroscopic observations during the outburst using instruments on the SOAR, Magellan, and VLT telescopes, including data from the ESO public survey VVVX-GalCen. We first identified the location of the outbursting source and disentangled it from nearby companions. We then measured the line-of-sight extinction by comparing spectroscopic features. The stellar parameters were then estimated from radial velocity, proper motions, and stellar evolution models. NEOWISE We found that SPICY 30021 is an optically obscured FUor with a line-of-sight (interstellar and circumstellar) extinction of A_V = 12.5 mag. The spectrum of SPICY 30021 closely resembles the spectra of classical FUors. Using various methods, we measured the distance of SPICY 30021 as 1.7 = 30 ̊m L_⊙, which is moderate for FUors. The quiescent near-infrared photometry is consistent with a young, 0.9 ̊m M_⊙ progenitor, although the mass remains dependent on the model and distance. kpc. The accretion luminosity of the outburst is L_ ̊m acc We confirm that SPICY 30021 is a bona fide FUor event. The mid-infrared precursor suggests an outside-in triggering mechanism.