  Possible M-type contact binaries were investigated by selecting W UMa-type
variables with orbital periods below the 0.22-day cutoff. Gaia parallaxes were
combined with Gaia and 2MASS photometry to obtain G and J-band absolute
magnitudes of 674 red variable stars catalogued as contact binaries in the VSX
database. The absolute magnitude of main sequence cool dwarfs varies strongly
with spectral type, which was used to create a selection of 218 systems with
primaries potentially of spectral types M0-M3. Lightcurves of the 46 systems
with lowest near-infrared luminosities were inspected individually to confirm
or reject the W UMa classification where possible. The extinction limits and
amplitudes were combined with the calculated absolute magnitudes in order to
set upper limits for the masses of the primary components. This is achieved via
the consideration that the luminosity of the primary is no less than that of a
main sequence star of the same mass. For 26 possible contact binaries the mass
of the primary was limited to less than 0.5 solar masses with some systems
having upper limits for the primary as low as 0.35 solar masses. These rare
systems are intriguing targets for more detailed observations since they are on
the low-mass end of the contact binary distribution and their formation and
evolution are still unclear.
