When Stars Mimic Monsters: Spectral Evidence for an <i>η</i> Carinae−like Giant Eruption in SBS 0335−052 E

Abstract SBS 0335−052 E is an extremely low metallicity ( Z ∼ 0.04 Z ⊙ ) blue compact dwarf galaxy. An active galactic nucleus has been proposed to explain the broad H α emission and near-infrared (NIR) time variability in super star clusters (SSCs) 1 and 2. However, Peng et al. discovered broad wings in the forbidden [O iii ] λ 5007 emission (up to ∼5,000 km s −1 ), challenging the broad-line region interpretation. We present new Keck Cosmic Web Imager/Keck Cosmic Reionization Mapper integral-field spectroscopy to directly compare spectra across multiple SSCs. The nebula surrounding SSCs 1 and 2 shows unique features. The Ly β -pumped O i λ 8446 emission constrains τ Ly α ∼ 10 8 . Multiple ionization states of iron are detected from Fe + to Fe +4 . Stellar photoionization models can reproduce the [Fe iii ]/[Fe ii ] and [Fe iv ]/[Fe iii ] line ratios at high density ( n e ∼ 10 6 cm −3 ), but they fail to account for most of the [Fe v ] emission. The broad H α wings exhibit an exponential profile; the asymmetric wings extend from ∼−5,000 to ∼10,000 km s −1 . Thomson scattering in a radially expanding medium provides a good fit with v w ∼ 200 km s −1 , optical depth τ e ∼ 10, and an outer-to-inner radius of 10. Enhanced N/O and potentially depleted Fe/O ratios are consistent with CNO-cycled ejecta from massive stars and with dust formation, respectively. We propose that mass loss from a massive star interacting with its circumstellar medium drives a shock that powers the NIR variability, the luminous X-ray point source, and the [Fe v ] emission. If confirmed, the proposed stellar eruption would be a distant example of an η Carinae−like giant eruption, and the first in an ultra−low-metallicity environment.