NGTS J214358.5-380102 -- NGTS discovery of the most eccentric known eclipsing M-Dwarf binary system
Abstract
We present the discovery of NGTS J214358.5-380102, an eccentric M-dwarf binary discovered by the Next Generation Transit Survey. The system period of 7.618 days is greater than many known eclipsing M-dwarf binary systems. Its orbital eccentricity of 0.323+0.0014-0.0037, is large relative to the period and semi-major axis of the binary. Global modelling of photometry and radial velocities indicate stellar masses of MA=0.426 +0.0056-0.0049, MB=0.455 +0.0058-0.0052 and stellar radii RA=0.461 +0.038-0.025 RB=0.411 +0.027-0.039, respectively. Comparisons with stellar models for low mass stars show that one star is consistent with model predictions whereas the other is substantially oversized. Spectral analysis of the system suggests a primary of spectral type M3V, consistent with both modelled masses and radii, and with SED fitting of NGTS photometry. As the most eccentric eclipsing M-dwarf binary known, NGTS J214358.5-380102 provides an interesting insight into the strength of tidal effects in the circularisation of stellar orbits.