Talk abstract details
CoRoT 101186644: A transiting low-mass dense M-dwarf on an eccentric 20.7-day period orbit around a late F-star
Abstract
We present the study of the CoRoT transiting planet candidate CoRoT 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$_{\rm eff}=6090\pm200$\,K) and a low-mass dense late M-dwarf secondary star on an eccentric ($e=0.4$) orbit with a period of $20.7$ days. The M-dwarf has a mass of $0.096\pm0.011$\,M$_{\odot}$, and a radius of $0.104_{-0.006}^{+0.026}$\,R$_{\odot}$, which makes it probably the smallest and most dense late M-dwarf reported so far. In addition, contrary to the well-known problem of inflated M-dwarfs, the radius of the secondary is probably consistent or might even be below the radius predicted by theoretical M-R models for M stars.
The high uncertainty of the secondary radius is due to the limited ability to place an upper limit on light contribution from a possible background star. Nevertheless, this discovery adds yet another piece to the puzzle of the mass-radius relations at the bottom of the main sequence.
We review the current agreement between observations and theory of very-low-mass stars (M\,$\lesssim0.2$\,M$_{\odot}$), and conclude that a large scatter of radii probably exists in this mass domain, but no clear discrepancy between models and observations can be deduced at this point.
The high uncertainty of the secondary radius is due to the limited ability to place an upper limit on light contribution from a possible background star. Nevertheless, this discovery adds yet another piece to the puzzle of the mass-radius relations at the bottom of the main sequence.
We review the current agreement between observations and theory of very-low-mass stars (M\,$\lesssim0.2$\,M$_{\odot}$), and conclude that a large scatter of radii probably exists in this mass domain, but no clear discrepancy between models and observations can be deduced at this point.