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

Abstract

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 μ Lep and β Scl, and to the superficially normal star ν Cap. In the spectra of the six stars, the Hg ii line at 3984 Å 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.

Keywords

• Eclipsing binary stars
• Chemically peculiar stars