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Possible M-type contact binaries were investigated by selecting W UMa-typevariables with orbital periods below the 0.22-day cutoff. Gaia parallaxes werecombined with Gaia and 2MASS photometry to obtain G and J-band absolutemagnitudes of 674 red variable stars catalogued as contact binaries in the VSXdatabase. The absolute magnitude of main sequence cool dwarfs varies stronglywith spectral type, which was used to create a selection of 218 systems withprimaries potentially of spectral types M0-M3. Lightcurves of the 46 systemswith lowest near-infrared luminosities were inspected individually to confirmor reject the W UMa classification where possible. The extinction limits andamplitudes were combined with the calculated absolute magnitudes in order toset upper limits for the masses of the primary components. This is achieved viathe consideration that the luminosity of the primary is no less than that of amain sequence star of the same mass. For 26 possible contact binaries the massof the primary was limited to less than 0.5 solar masses with some systemshaving upper limits for the primary as low as 0.35 solar masses. These raresystems are intriguing targets for more detailed observations since they are onthe low-mass end of the contact binary distribution and their formation andevolution are still unclear.

Ultra-short period contact binaries: restricting the parameters of the primary using Gaia parallax