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

We present the radial-velocity follow-up of two Kepler planetary transitingcandidates (KOI-189 and KOI-686) carried out with the SOPHIE spectrograph atthe Observatoire de Haute Provence. These data promptly discard these objectsas viable planet candidates and show that the transiting objects are in theregime of very low-mass stars, where a strong discrepancy between observationsand models persists for the mass and radius parameters. By combining the SOPHIEspectra with the Kepler light curve and photometric measurements found in theliterature, we obtain a full characterization of the transiting companions,their orbits, and their host stars. The two companions are in significantlyeccentric orbits with relatively long periods (30 days and 52.5 days), whichmakes them suitable objects for a comparison with theoretical models, since theeffects invoked to understand the discrepancy with observations are weaker forthese orbital distances. KOI-189 B has a mass M = 0.0745 +/- 0.0033 Msun and aradius R = 0.1025 +/- 0.0024 Rsun. The density of KOI-189 B is significantlylower than expected from theoretical models for a system of its age. We explorepossible explanations for this difference. KOI-189 B is the smallesthydrogen-burning star with such a precise determination of its fundamentalparameters. KOI-686 B is larger and more massive (M = 0.0915 +/- 0.0043 Msun; R= 0.1201 +/- 0.0033 Rsun), and its position in the mass-radius diagram agreeswell with theoretical expectations.

SOPHIE velocimetry of Kepler transit candidates. XIII. KOI-189 B and KOI-686 B: two very low-mass stars in long-period orbits