We have discovered a new , near-equal mass , eclipsing M dwarf binary from the Next Generation Transit Survey .
This system is only one of 3 field age ( > 1 Gyr ) , late M dwarf eclipsing binaries known , and has a period of 1.74774 days , similar to that of CM Dra and KOI126 .
Modelling of the eclipses and radial velocities shows that the component masses are M _ { pri } = 0.17391 ^ { +0.00153 } _ { -0.00099 } M _ { \odot } , M _ { sec } = 0.17418 ^ { +0.00193 } _ { -0.00059 } M _ { \odot } ; radii are R _ { pri } = 0.2045 ^ { +0.0038 } _ { -0.0058 } R _ { \odot } , R _ { sec } = 0.2168 ^ { +0.0047 } _ { -0.0048 } .
The effective temperatures are T _ { pri } = 2995 ^ { +85 } _ { -105 } K and T _ { sec } = 2997 ^ { +66 } _ { -101 } K , consistent with M5 dwarfs and broadly consistent with main sequence models .
This pair represents a valuable addition which can be used to constrain the mass-radius relation at the low mass end of the stellar sequence .