Letter to the Editor Emission lines in the spectra of late-B type stars

We report detections of weak emission lines in the red spectral region of sharp-lined chemically normal and peculiar (HgMn) late-B type stars from high spectral resolution and high signal-to-noise data. Most emission lines originate from high-excitation states of the ions Cr II and Mn II, with others likely to be attributed to Ti II and Fe II. The emission is observed to extend over the entire line profile width for rotational velocities up to 18 km s−1, implying that it originates within the same rotational framework as the absorption line spectrum. Within the sample no obvious correlation is noted for the presence of emission with regard to stellar effective temperature or luminosity. A dependence upon element abundance is evident from the absence of Mn II emission for HgMn stars for which the manganese enhancement is greater than 1.3 dex. This trend is mildly reinforced by the chromium emission spectrum being most developed amongst stars richer in chromium. We postulate that the Cr II and Mn II emissions in the red spectral region arise from a selective excitation process involving hydrogen Lyα photon energies.