EBLM XV – revised dynamical masses for the circumbinary planet host Kepler-16 AB, using the SOPHIE spectrograph

ABSTRACT Eclipsing binaries are perfect laboratories to measure precise, accurate and model-independent stellar radii and stellar masses, so long as both components are spectroscopically resolved. Resolving both components is difficult in high-contrast binaries, for instance, those composed of an FGK main-sequence star with an M-type companion. In those cases, the secondary can contribute $<1~{{\ \rm per\ cent}}$ of the total flux in optical wavelengths. This makes measuring dynamical masses challenging and has typically only been attempted with large-aperture telescopes (8–10 m). The High-Resolution Cross-Correlation Spectroscopy (HRCCS) method was developed to extract weak emission and transmission spectra for exoplanet atmospheres. This method was recently adapted and applied to measure dynamical masses in high-contrast binaries. In this work, we apply the HRCCS method to optical spectra of the high-contrast binary and circumbinary planet host Kepler-16 AB, obtained with the SOPHIE spectrograph at the 1.93-m telescope at the Observatoire de Haute-Provence. The secondary, which has a contrast ratio of $\sim 6 \times 10^{-3}$, is resolved with a detection significance of 9.5$\sigma$. We derive dynamical masses with a precision of $1.5~{{\ \rm per\ cent}}$ and $0.9~{{\ \rm per\ cent}}$ for the primary and secondary, respectively. These are comparable, but slightly higher (within $2\!-\!7~{{\ \rm per\ cent}}$), to previous mass-measurements, which has -within the uncertainties- no implication for the mass of the known circumbinary planet. This work demonstrates that dynamical mass measurements of high-contrast binaries can be done with 2-m class telescopes. We also investigate different analysis protocols to ensure we derive robust uncertainties for dynamical masses.