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 $M_{rm pri}$=0.17391$^{+0.00153}_{0.00099}$ $M_{odot}$, $M_{rm sec}$=0.17418$^{+0.00193}_{-0.00059}$ $M_{odot}$; radii are $R_{rm pri}$=0.2045$^{+0.0038}_{-0.0058}$ $R_{odot}$, $R_{rm sec}$=0.2168$^{+0.0047}_{-0.0048}$ $R_{odot}$. The effective temperatures are $T_{rm pri} = 2995,^{+85}_{-105}$ K and $T_{rm sec} = 2997,^{+66}_{-101}$ 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.
Download