Xenon in Mercury-Manganese Stars

TL;DR

This study reveals that xenon is vastly over-abundant in most Mercury-Manganese stars, using high-resolution spectroscopy and LTE abundance analysis, highlighting the importance of specific spectral lines for detection.

Contribution

It provides the first extensive detection and quantification of xenon over-abundance in HgMn stars using modern spectral analysis techniques.

Findings

Xenon is over-abundant by 3.1–4.8 dex in 21 of 22 HgMn stars studied.

No significant correlation between Xe abundance and stellar temperature (Teff).

Normal late B stars show no detectable Xe II lines, confirming over-abundance in HgMn stars.

Abstract

Previous studies of elemental abundances in Mercury-Manganese (HgMn) stars have occasionally reported the presence of lines of the ionized rare noble gas Xe II, especially in a few of the hottest stars with Teff ~ 13000--15000 K. A new study of this element has been undertaken using observations from Lick Observatory's Hamilton Echelle Spectrograph. In this work, the spectrum synthesis program UCLSYN has been used to undertake abundance analysis assuming LTE. We find that in the Smith & Dworetsky sample of HgMn stars, Xe is vastly over-abundant in 21 of 22 HgMn stars studied, by factors of 3.1--4.8 dex. There does not appear to be a significant correlation of Xe abundance with Teff. A comparison sample of normal late B stars shows no sign of Xe II lines that could be detected, consistent with the expected weakness of lines at normal abundance. The main reason for the previous lack of widespread detection in HgMn stars is probably due to the strongest lines being at longer wavelengths than the photographic blue. The lines used in this work were 4603.03A, 4844.33A and 5292.22A.