The Surface Composition of Six Newly Discovered Chemically Peculiar Stars. Comparison to the HgMn Stars mu Lep and beta Scl and the Superficially Normal B Star nu Cap

We report on a detailed abundance study of six bright, mostly southern, slowly rotating late B-stars: HD 1279 (B8III), HD 99803 (B9V), HD 123445 (B9V), HD 147550 (B9V), HD 171961 (B8III), and HD 202671 (B5II/III), hitherto reported as normal stars. We compare them to the two classical HgMn stars mu Lep and beta Scl, and to the superficially normal star nu Cap. In the spectra of the six stars, the Hg II line at 3984 angstrom line is clearly seen and numerous lines of P, Ti, Mn, Fe, Ga, Sr, Y, and Zr appear to be strong absorbers. A comparison of newly acquired and archival spectra of these objects with a grid of synthetic spectra for selected unblended lines reveals large overabundances of P, Ti, Cr, Mn, Sr, Y, Zr, Ba, Pt, and Hg, and underabundances of He, Mg, Sc, and Ni. The effective temperatures, surface gravities, low projected rotational velocities, and the peculiar abundance patterns of the six investigated stars show that they are new chemically peculiar stars, mostly new HgMn stars, and are reclassified as such. The evolutionary status of these stars has been inferred, and their ages and masses estimated. The two most massive objects, HD 1279 and HD 202671, might have evolved away from the main sequence recently, the other stars are main-sequence objects. HD 99803A is a sharp lined HgMn star with grazing eclipses. From TESS and MASCARA photometry, we determine an orbital period of P-orb = 26.12022 +/- 0.00004 day.

Automated summary

In this study, we conducted a detailed abundance analysis of six bright, slowly rotating late B-stars. The spectra of these stars revealed the presence of Hg II lines and strong absorption lines from various elements. Comparisons with synthetic spectra showed significant overabundances of certain elements and underabundances of others. The investigated stars were found to be new chemically peculiar stars, most of which are new HgMn stars. The evolutionary status, ages, and masses of these stars were determined, and their orbital period was measured for HD 99803A.