The masses and radii of HD186753B and TYC7096-222-1B: the discovery of two M-dwarfs that eclipse A-type stars

Abstract

We present observations of two new single-lined eclipsing binaries, both consisting of an Am star and an M-dwarf, discovered by the Wide Angle Search for Planets transit photometry survey. Using WASP photometry and spectroscopic measurements we find that HD186753B has an orbital period of P=1.9194 days, a mass of M=0.24 +/- 0.02 M_sun and radius of R=0.31 +/- 0.06 R_sun; and that TCY7096-222-1B has an orbital period of P=8.9582 days, a mass between 0.29 and 0.54 M_sun depending on eccentricity and radius of R=0.263+0.02-0.07 R_sun. We find that the Am stars have relatively low rotational velocities that closely match the orbital velocities of the M-dwarfs, suggesting that they have been "spun-down" by the M-dwarfs.

5 pages, 3 figures, 3 tables

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• The Implications of M Dwarf Flares on the Detection and Characterization of Exoplanets at Infrared Wavelengths
• CoRoT 101186644: A transiting low-mass dense M-dwarf on an eccentric 20.7-day period orbit around a late F-star
• Revising the properties of low mass eclipsing binary stars using TESS light curves