A reappraisal of the gap in the HR diagram of M67

Consideration of the effects of unresolved binaries and observational errors, and careful application of the Schwarzschild criterion at the boundary of the convective core, show that the observed HR diagram of M67 can be remodelled with stars computed conventionally, i.e. without using convective overshooting. The computed isochrone is used to show that M67 may have a constant mass function. (author)