English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The spectra of helium-dominated white dwarf stars with hydrogen in theiratmosphere present a distinctive broad feature centered around 1160~\AA\/ inthe blue wing of the Lyman-$\alpha$ line. It is extremely apparent in WD1425+540 recently observed with HST COS. With new theoretical line profilesbased on ab initio atomic interaction potentials we show that this feature is asignature of a collision-induced satellite due to an asymptotically forbiddentransition. This quasi-molecular spectral satellite is crucial to understandingthe asymmetrical shape of Lyman-$\alpha$ seen in this and other white dwarfspectra. Our previous work predicting this absorption feature was limited bymolecular potentials that were not adequate to follow the atomic interactionswith spectroscopic precision to the asymptotic limit of large separation. A newset of potential energy curves and electronic dipole transition moments for thelowest electronic states of the H--He system were developed to accountaccurately for the behavior of the atomic interactions at all distances, fromthe chemical regime within 1~\AA\/ out to where the radiating H atoms are notsignificantly perturbed by their neighbors. We use a general unified theory ofcollision-broadened atomic spectral lines to describe a rigorous treatment ofhydrogen Lyman-$\alpha$ with these potentials and present a new study of itsbroadening by radiative collisions of hydrogen and neutral helium. Theseresults enable ab initio modeling of radiative transport in DBA white dwarfatmospheres.

H--He collision-induced satellite in the Lyman-$\alpha$ profile of DBA white dwarf stars