M dwarf stars rotational broadening measurements

A proposed explanation for this discrepancy involves effects from strong magnetic fields, induced by rapid rotation via the dynamo process. Although, a handful of single, slowly rotating M dwarfs with radius measurements from interferometry also appear to be larger than models predict, suggesting that rotation or binarity specifically may not be the sole cause of the discrepancy.

We test whether single, rapidly rotating, fully convective stars are also larger than expected by measuring their Rsini distribution. We combine photometric rotation periods from the literature with rotational broadening (vsini) measurements reported in this work for a sample of 88 rapidly rotating M dwarf stars. Using a Bayesian framework, we find that stellar evolutionary models underestimate the radii by 10%-15%_-2.5_^+3^, but that at higher masses (0.18<M<0.4 M_Sun_), the discrepancy is only about 6% and comparable to results from interferometry and eclipsing binaries.