We present quasar bolometric corrections using the [O III] $lambda5007$ narrow emission line luminosity based on the detailed spectral energy distributions of 53 bright quasars at low to moderate redshift ($0.0345<z<1.0002$). We adopted two functional forms to calculate $L_{textrm{iso}}$, the bolometric luminosity determined under the assumption of isotropy: $L_{textrm{iso}}=A,L_{[O,III]}$ for comparison with the literature and log$(L_{iso})=B+C,$log$(L_{[O,III]})$, which better characterizes the data. We also explored whether Eigenvector 1, which describes the range of quasar spectral properties and quantifies their diversity, introduces scatter into the $L_{[O,III]}-L_{iso}$ relationship. We found that the [O III] bolometric correction can be significantly improved by adding a term including the equivalent width ratio $R_{Fe,II}equiv EW_{Fe,II}/EW_{Hbeta}$, which is an Eigenvector 1 indicator. Inclusion of $R_{Fe,II}$ in predicting $L_{iso}$ is significant at nearly the $3sigma$ level and reduces the scatter and systematic offset of the luminosity residuals. Typically, [O III] bolometric corrections are adopted for Type 2 sources where the quasar continuum is not observed and in these cases, $R_{Fe,II}$ cannot be measured. We searched for an alternative measure of Eigenvector 1 that could be measured in the optical spectra of Type 2 sources but were unable to identify one. Thus, the main contribution of this work is to present an improved [O III] bolometric correction based on measured bolometric luminosities and highlight the Eigenvector 1 dependence of the correction in Type 1 sources.
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