calibration sample [@Dopita00; @Kewley02; @Steidel14].

Recently, several studies have shown that stacking the spectra of a sufficiently large number of galaxies can boost the S/N of the auroral lines to a detectable level [@Liang07; @Andrews13]. We use the stacking technique presented in @Andrews13 to obtain direct method oxygen abundances for galaxies spanning a wide range in ${\hbox{$M_{\star}$}}$ and SFR. Our stacking method mitigates the potential for bias by binning galaxies we expect to have similar metallicities based on the small intrinsic scatter of the MZR and ${\hbox{$M_{\star}$--$Z$--${\rm SFR}$}}$ relation. We then recalibrate the popular strong line abundance diagnostics with the direct method oxygen abundances, and apply the new calibrations to data taken from the literature.

We adopt the following notation for the principal diagnostic emission line ratios:

& =  6583 / &\
& =  5007 / /  6583 / &\
& =  6583 /  3727 &\
&R\_2=  3727 / &\
&R\_3=  4959,5007 / &\
&R\_[23]{} = R\_2+R\_3 &\
&P = R\_3/R\_[23]{} &\

Section \[sec:data\] describes our selection and stacking process. Section \[sec:analysis\] describes our empirical calibrations of . In Section \[sec:results\] we present our newly derived calibrations. In Section \[sec:discussion\] we apply our calibrations to various samples of galaxies and 