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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

A dozen short-period detached binaries are known to host transitingcircumbinary planets. In all circumbinary systems so far, the planetary andbinary orbits are aligned within a couple of degrees. However, the obliquity ofthe primary star, which is an important tracer of their formation, evolution,and tidal history, has only been measured in one circumbinary system until now.EBLM J0608-59/TOI-1338 is a low-mass eclipsing binary system with a recentlydiscovered circumbinary planet identified by TESS. Here, we performhigh-resolution spectroscopy during primary eclipse to measure the projectedstellar obliquity of the primary component. The obliquity is low, and thus theprimary star is aligned with the binary and planetary orbits with a projectedspin-orbit angle $\beta = 2.8 \pm 17.1$ deg. The rotation period of $18.1 \pm1.6$ days implied by our measurement of $v\sin{i_\star}$ suggests that theprimary has not yet pseudo-synchronized with the binary orbit, but isconsistent with gyrochronology and weak tidal interaction with the binarycompanion. Our result, combined with the known coplanarity of the binary andplanet orbits, is suggestive of formation from a single disc. Finally, weconsidered whether the spectrum of the faint secondary star could affect ourmeasurements. We show through simulations that the effect is negligible for oursystem, but can lead to strong biases in $v\sin{i_\star}$ and $\beta$ forhigher flux ratios. We encourage future studies in eclipse spectroscopy testthe assumption of a dark secondary for flux ratios $\gtrsim 1$ ppt.

The EBLM project. VII. Spin-orbit alignment for the circumbinary planet host EBLM J0608-59 A/TOI-1338 A