Annihilation during positron-hydrogen collisions: Addendum and erratum

The $p$-wave contribution to the positron-hydrogen annihilation rate, in terms of $Z_{\mathrm{eff}}$, is corrected from a previous calculation of the authors, thereby removing the discrepancy with later calculations of Chan and McEachran. The present results should be the most accurate available. This opportunity is taken to give thermally averaged positron-hydrogen annihilation coefficients $\overline{Z}\mathrm{}\left(T\right)\mathrm{}$, which are of use in the analysis of solar-flare observations of the positron-electron annihilation line. For reference and experimental purposes we also present curves of the integrated elastic and momentum-transfer (i.e., diffusion) cross sections, as well as effective cross sections which account for the finite acceptance angle of the detector.