CM Draconis: another study, another solution...

Lazarus · by Lazarus on Sat Oct 11, 2008 6:38 pm

Absolute properties of the low-mass eclipsing binary CM Draconis

The companion postulated in this paper does not seem to have been confirmed.

Deeg et al. (2008) have recently reported the possible presence of a third body around CM Dra based on a parabolic fit to their sample of (O − C) values. We find, however, that using our own timings a parabolic fit is essentially indistinguishable from a linear fit to the measurements. Thus, any third body must have a period longer than roughly twice the span of the measurements, or ∼60 years, or must induce a light-time effect below ∼ 15 s which would be undistinguishable from the dispersion of the data due to spot effects.

Instead the eccentricity of the CM Draconis binary, combined with constraints on orbital stability and transit timing suggest that there might be a substellar object (a giant planet or a brown dwarf) in orbit in the 50-200 day period range.