* Astronomy

Title: The Masses and Radii of HD186753B and TYC7096-222-1B: The First M-dwarfs known to Eclipse A-type Stars
Authors: S. J. Bentley, B. Smalley, P. F. L. Maxted, C. Hellier, D. M. Wilson, D. R. Anderson, A. Collier Cameron, M. Gillon, L. Hebb, D. L. Pollacco, D. Queloz, A. H. M. J. Triaud, R. G. West
(Version v2)

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 solar masses and radius of R=0.31^{+0.06}_{-0.06} solar radii; and that TCY7096-222-1B has an orbital period of P=8.9582 days, a mass of between 0.29 and 0.54 solar masses depending on eccentricity and radius of R=0.263^{+0.02}_{-0.07} solar radii. 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.

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