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

As a result of competing physical mechanisms, the atmospheric composition ofwhite dwarfs changes throughout their evolution, a process known as spectralevolution. Because of the ambiguity of their atmospheric compositions and thedifficulties inherent to the modeling of their dense atmospheres, no consensusexists regarding the spectral evolution of cool white dwarfs ($T_{\rmeff}<6000$ K). In the previous papers of this series, we presented andobservationally validated a new generation of cool white dwarf atmospheremodels that include all the necessary constitutive physics to accurately modelthose objects. Using these new models and a homogeneous sample of 501 coolwhite dwarfs, we revisit the spectral evolution of cool white dwarfs. Oursample includes all spectroscopically identified white dwarfs cooler than 8300K for which a parallax is available in Gaia DR2 and photometric observationsare available in Pan-STARRS1 and 2MASS. Except for a few cool carbon-pollutedobjects, our models allow an excellent fit to the spectroscopic and photometricobservations of all objects included in our sample. We identify a decrease ofthe ratio of hydrogen to helium-rich objects between 7500 K and 6250 K, whichwe interpret as the signature of convective mixing. After this decrease,hydrogen-rich objects become more abundant up to 5000 K. This puzzlingincrease, reminiscent of the non-DA gap, has yet to be explained. At lowertemperatures, below 5000 K, hydrogen-rich white dwarfs become rarer, whichrules out the scenario according to which accretion of hydrogen from theinterstellar medium dominates the spectral evolution of cool white dwarfs.

A New Generation of Cool White Dwarf Atmosphere Models. IV. Revisiting the Spectral Evolution of Cool White Dwarfs