We present the study of the CoRoT transiting planet candidate 101186644, also named LRc01_E1_4780. Analysis of the CoRoT lightcurve and the HARPS spectroscopic follow-up observations of this faint... Show moreWe present the study of the CoRoT transiting planet candidate 101186644, also named LRc01_E1_4780. Analysis of the CoRoT lightcurve and the HARPS spectroscopic follow-up observations of this faint (m$_V$ = 16) candidate revealed an eclipsing binary composed of a late F-type primary (T$_{eff}$ = 6090 {plusmn} 200 K) and a low-mass, dense late M-dwarf secondary on an eccentric (e = 0.4) orbit with a period of ~{}20.7 days. The M-dwarf has a mass of 0.096 {plusmn} 0.011 M$_{⊙}$, and a radius of 0.104$_{-0.006}$$^{+0.026}$ R$_{⊙}$, which possibly makes it the smallest and densest late M-dwarf reported so far. Unlike the claim that theoretical models predict radii that are 5-15% smaller than measured for low-mass stars, this one seems to have a radius that is consistent and might even be below the radius predicted by theoretical models. Based on observations made with the 1-m telescope at the Wise Observatory, Israel, the Swiss 1.2-m Leonhard Euler telescope at La Silla Observatory, Chile, the IAC-80 telescope at the Observatory del Teide, Canarias, Spain, and the 3.6-m telescope at La Silla Observatory (ESO), Chile (program 184.C-0639). Show less
