New line identifications in the blue spectra of Hg–Mn stars

A card catalogue of previously unidentified lines between 3755 and 4650 Å in the spectra of eight sharp-lined Hg–Mn stars (112 Her pr, HR 7361, 7245, 7143, χ Lup pr, 28 Her, HR 4072 pr and HR 7775) was compiled. Counts of known lines of the elements in each star were used in conjunction with recent laboratory data to propose nearly 100 new line identifications. These include additional lines of P II, Cr II, Mn II and Fe II, high-excitation lines of Ti II and Y II, several Au II and Pt I lines and a resonance line of Tl I 3775.72 Å in HR 7775, and a Cu II line at 4043.51 Å in HR 7361. Two weak lines in the cool stars χ Lup pr and HR 4072 pr were identified as P II. An interesting result is the detection of lines of the adjacent rare-earth elements Pr and Nd in HR 7775, despite the absence of Eu II lines. No definite identifications of rare-earth lines have previously been made in Hg–Mn stars, although Bidelman noted that Pr III lines are probably present in χ Lup.