2016AJ....151...84E

Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system for a better understanding of the low-mass end of the Hertzsprung-Russel diagram. We used photometric light curves and radial velocity follow-up measurements to study the binary. Spectroscopic analysis was used in combination with isochrone fitting to characterize the primary star. The primary star is an early F-type main-sequence star with a mass of (1.493±0.073) M_☉ and a radius of (1.474±0.040) R_☉. The companion is an M dwarf with a mass of (0.188±0.014) M_☉and a radius of (0.234±0.009) R_☉. The orbital period is (1.35121±0.00001) days. The secondary star is among the lowest-mass M dwarfs known to date. The binary has not reached a 1:1 spin-orbit synchronization. This indicates a young main-sequence binary with an age below ∼250 Myr. The mass-radius relation of both components are in agreement with this finding.