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 recently discovered subdwarf B (sdB) pulsator KIC7668647 is one of the 18pulsating sdB stars detected in the Kepler field. It features a rich g-modefrequency spectrum, with a few low-amplitude p-modes at short periods.  We use new ground-based low-resolution spectroscopy, and the near-continuous2.88 year Kepler lightcurve, to reveal that KIC7668647 consists of a subdwarf Bstar with an unseen white-dwarf companion with an orbital period of 14.2d. Anorbit with a radial-velocity amplitude of 39km/s is consistently determinedfrom the spectra, from the orbital Doppler beaming seen by Kepler at 163ppm,and from measuring the orbital light-travel delay of 27 by timing of the manypulsations seen in the Kepler lightcurve. The white dwarf has a minimum mass of0.40 M_sun.  We use our high signal-to-noise average spectra to study the atmosphericparameters of the sdB star, and find that nitrogen and iron have abundancesclose to solar values, while helium, carbon, oxygen and silicon areunderabundant relative to the solar mixture.  We use the full Kepler Q06--Q17 lightcurve to extract 132 significantpulsation frequencies. Period-spacing relations and multiplet splittings allowus to identify the modal degree L for the majority of the modes. Using theg-mode multiplet splittings we constrain the internal rotation period at thebase of the envelope to 46-48d as a first seismic result for this star. The fewp-mode splittings may point at a slightly longer rotation period further out inthe envelope of the star.  From mode-visibility considerations we derive that the inclination of therotation axis of the sdB in KIC7668647 must be around ~60 degrees.  Furthermore, we find strong evidence for a few multiplets indicative ofdegree 3 <= L <= 8, which is another novelty in sdB-star observations madepossible by Kepler.

KIC7668647: a 14 day beaming sdB+WD binary with a pulsating subdwarf