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

Near-infrared interferometers have recently imaged a number of rapidlyrotating A-type stars, finding levels of gravity darkening inconsistent withtheoretical expectations. Here, we present new imaging of both a cooler star{\beta} Cas (F2IV) and a hotter one {\alpha} Leo (B7V) using the CHARA arrayand the MIRC instrument at the H band. Adopting a solid-body rotation modelwith a simple gravity darkening prescription, we modeled the stellar geometricproperties and surface temperature distributions, confirming both stars arerapidly rotating and show gravity darkening anomalies. We estimate the massesand ages of these rapid rotators on L-Rpol and HR diagrams constructed fornon-rotating stars by tracking their non-rotating equivalents. The unexpectedfast rotation of the evolved subgiant {\beta} Cas offers a unique test of thestellar core-envelope coupling, revealing quite efficient coupling over thepast ~ 0.5 Gyr. Lastly we summarize all our interferometric determinations ofthe gravity darkening coefficient for rapid rotators, finding none match theexpectations from the widely used von Zeipel gravity darkening laws. Since theconditions of the von Zeipel law are known to be violated for rapidly rotatingstars, we recommend using the empirically-derived {\beta} = 0.19 for such starswith radiation-dominated envelopes. Furthermore, we note that no paradigmexists for self-consistently modeling heavily gravity-darkened stars that showhot radiative poles with cool convective equators.

Colder and Hotter: Interferometric imaging of {\beta} Cassiopeiae and {\alpha} Leonis