Atomic diffusion in the atmosphere of Feige 86

TL;DR

This paper revisits the spectral analysis of Feige 86, revealing its cooler, more compact nature and highlighting the role of atomic diffusion in its atmosphere, which is crucial for understanding hot subdwarf stars.

Contribution

It provides new insights into Feige 86's physical properties and emphasizes the importance of high-resolution UV spectroscopy to study atomic diffusion in stellar atmospheres.

Findings

Feige 86 is cooler and more compact than previously thought.

Numerous unidentified heavy metal lines indicate efficient atomic diffusion.

Highlights the need for high-resolution UV spectroscopy to test diffusion theories.

Abstract

We have revisited the ultraviolet and optical spectra of the blue horizontal branch star Feige 86. The new analysis finds the star cooler and more compact than previously determined. The IUE spectrum of Feige 86 holds numerous unidentified spectral lines of heavy metals, indicating efficient atomic diffusion in the atmosphere. Because diffusion plays a key role in the atmospheres of hot subdwarfs as well, it is indispensable to a better understanding of subdwarf pulsations and evolution. Feige 86 looks like an ideal target to confront diffusion theory with observations and test spectroscopic techniques. Therefore, to advance our general understanding of diffusion in stellar atmospheres we urge for new ultraviolet spectroscopy of Feige 86 at the highest possible resolution with HST/STIS.