First detection of bromine and antimony in hot stars

TL;DR

This paper reports the first detection of bromine and antimony in hot stars, specifically in helium-rich white dwarfs, using far-ultraviolet spectra and precise laboratory data to identify spectral lines.

Contribution

It provides the first identification of bromine and antimony in hot stars, correcting previous misidentifications and demonstrating radiative levitation effects in white dwarf atmospheres.

Findings

First detection of Br and Sb in hot stars.

Identification of specific spectral lines for Br VI and Sb V/VI.

Evidence of oversolar abundances caused by atomic diffusion.

Abstract

Bromine (atomic number Z=35) and antimony (Z=51) are extremely difficult to detect in stars. In very few instances, weak and mostly uncertain identifications of Br I, Br II, and Sb II in relatively cool, chemically peculiar stars were successful. Adopted solar abundance values rely on meteoritic determinations. Here, we announce the first identification of these species in far-ultraviolet spectra of hot stars (with effective temperatures of 49,500-70,000 K), namely in helium-rich (spectral type DO) white dwarfs. We identify the Br VI resonance line at 945.96 A. A previous claim of Br detection based on this line is incorrect because its wavelength position is inaccurate by about 7 A in atomic databases. Taking advantage of precise laboratory measurements, we identify this line as well as two other, subordinate Br VI lines. Antimony is detected by the Sb V resonance doublet at 1104.23/1225.98 A, as well as two subordinate Sb VI lines. A model-atmosphere analysis reveals strongly oversolar Br and Sb abundances that are caused by radiative-levitation dominated atomic diffusion.