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

White dwarfs (WDs) that accrete helium at rates $\sim 10^{-8} \, M_\odot \,\rm yr^{-1}$, such as those in close binaries with sdB stars, can accumulatelarge ($\gtrsim 0.1 \, M_\odot$) helium envelopes which are likely to detonate.We perform binary stellar evolution calculations of sdB+WD binary systems withMESA, incorporating the important reaction chain $^{14}{\rm N}(e^-, \nu){^{14}{\rm C}} ( \alpha, \gamma) {^{18}{\rm  O}}$ (NCO), including a recent measurement for the ${^{14}{\rm C}} ( \alpha,\gamma) {^{18}{\rm O}}$ rate. In large accreted helium shells, the NCO reactionchain leads to ignitions at the dense base of the freshly accreted envelope, incontrast to $3\alpha$ ignitions which occur away from the base of the shell. Inaddition, at these accretion rates, the shells accumulate on a timescalecomparable to their thermal time, leading to an enhanced sensitivity of theoutcome on the accretion rate history. Hence, time dependent accretion ratesfrom binary stellar evolution are necessary to determine the helium layer massat ignition. We model the observed sdB+WD system ${\rm CD}\,-30^\circ 11223$and find that the inclusion of these effects predicts ignition of a $0.153 \,M_\odot$ helium shell, nearly a factor of two larger than previous predictions.A shell with this mass will ignite dynamically, a necessary condition for ahelium shell detonation.

Electron Captures on $^{14}{\rm N}$ as a Trigger for Helium Shell Detonations