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The massive black hole (BH) population in dwarf galaxies ($M_{\rm BH}\lesssim 10^5~M_\odot$) can provide strong constraints on the origin of BHseeds. However, traditional optical searches for active galactic nuclei (AGNs)only reliably detect high-accretion, relatively high-mass BHs in dwarf galaxieswith low amounts of star formation, leaving a large portion of the overall BHpopulation in dwarf galaxies relatively unexplored. Here, we present a sampleof 81 dwarf galaxies ($M_\star \le 3 \times 10^9~M_\odot$) with detectable [FeX]$\lambda$6374 coronal line emission indicative of accretion onto massive BHs,only two of which were previously identified as optical AGNs. We analyzeoptical spectroscopy from the Sloan Digital Sky Survey and find [FeX]$\lambda$6374 luminosities in the range $L_{\rm[Fe\,X]}\approx10^{36}$-$10^{39}$ erg s$^{-1}$, with a median value of $1.6\times 10^{38}$ erg s$^{-1}$. The [Fe X]$\lambda$6374 luminosities aregenerally much too high to be produced by stellar sources, including luminousType IIn supernovae (SNe). Moreover, based on known SNe rates, we expect atmost 8 Type IIn SNe in our sample. On the other hand, the [Fe X]$\lambda$6374luminosities are consistent with accretion onto massive BHs from AGNs or tidaldisruption events (TDEs). We find additional indicators of BH accretion in somecases using other emission line diagnostics, optical variability, X-ray andradio emission (or some combination of these). However, many of the galaxies inour sample only have evidence for a massive BH based on their [FeX]$\lambda$6374 luminosities. This work highlights the power of coronal lineemission to find BHs in dwarf galaxies missed by other selection techniques andto probe the BH population in bluer, lower mass dwarf galaxies.

A Sample of Massive Black Holes in Dwarf Galaxies Detected via [Fe X] Coronal Line Emission: Active Galactic Nuclei and/or Tidal Disruption Events