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In contrast to massive galaxies with Solar or super-Solar gas phasemetallicities, very few Active Galactic Nuclei (AGN) are found inlow-metallicity dwarf galaxies. Such a population could provide insight intothe origins of supermassive black holes. Here we report near-infraredspectroscopic and X-ray observations of SDSS J105621.45+313822.1, a low-mass,low-metallicity galaxy with optical narrow line ratios consistent with starforming galaxies but a broad H$\alpha$ line and mid-infrared colors consistentwith an AGN. We detect the [Si VI] 1.96$\mu$m coronal line and a broadPa$\alpha$ line with a FWHM of $850 \pm 25$~km~s$^{-1}$. Together with theoptical broad lines and coronal lines seen in the SDSS spectrum, we confirm thepresence of a highly accreting black hole with mass $(2.2 \pm 1.3) \times10^{6}$~M$_{\odot}$, with a bolometric luminosity of$\approx10^{44}$~erg~s$^{-1}$ based on the coronal line luminosity, implying ahighly accreting AGN. Chandra observations reveal a weak nuclear point sourcewith $L_{\textrm{X,2-10 keV}} = (2.3 \pm 1.2) \times 10^{41}$~erg~s$^{-1}$,$\sim 2$ orders of magnitude lower than that predicted by the mid-infraredluminosity, suggesting that the AGN is highly obscured despite showing broadlines in the optical spectrum. The low X-ray luminosity and optical narrow lineratios of J1056+3138 highlight the limitations of commonly employed diagnosticsin the hunt for AGNs in the low metallicity low mass regime.

Multi-wavelength observations of SDSS J105621.45+313822.1, a broad-line, low-metallicity AGN