A low-mass eclipsing binary within the fully convective zone from the Next Generation Transit Survey
Bouchy, F.; Queloz, D.; Smith, A. M. S.; Günther, Maximilian N.; Louden, T.; Wheatley, P. J.; Gillen, E.; Goad, M. R.; McCormac, J.; West, R. G.; Poppenhaeger, K.; Casewell, S. L.; Watson, C. A.; Nielsen, L. D.; Jenkins, J. S.; Bayliss, D.; Burleigh, M. R.; Moyano, M.; Thompson, A.; Belardi, C.; Chaushev, A.; Raynard, L.; Eigmüller, Ph; de Mooij, E.; Jackman, J. A. G.
United Kingdom, Switzerland, Germany, Chile
Abstract
We have discovered a new, near-equal-mass, eclipsing M dwarf binary from the Next Generation Transit Survey. This system is only one of three field-age (>1 Gyr), late M dwarf eclipsing binaries known, and has a period of 1.74774 d, similar to that of CM Dra and KOI126. Modelling of the eclipses and radial velocities shows that the component masses are Mpri =0.17391 ^{+0.00153}_{-0.00099} M⊙, Msec = 0.17418 ^{+0.00193}_{-0.00059} M⊙; and the radii are Rpri = 0.2045 ^{+0.0038}_{-0.0058} R⊙, Rsec= 0.2168 ^{+0.0047}_{-0.0048} R⊙. 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 that can be used to constrain the mass-radius relationship at the low-mass end of the stellar sequence.