EDP Sciences
Free access
Volume 508, Number 1, December II 2009
Page(s) 391 - 394
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361/200913154
Published online 08 October 2009
A&A 508, 391-394 (2009)
DOI: 10.1051/0004-6361/200913154

Research Note

The masses and radii of HD 186753B and TYC7096-222-1B: the discovery of two M-dwarfs that eclipse A-type stars

S. J. Bentley1, B. Smalley1, P. F. L. Maxted1, C. Hellier1, D. M. Wilson1, 2, D. R. Anderson1, A. Collier Cameron3, M. Gillon4, 5, L. Hebb3, 6, D. L. Pollacco7, D. Queloz4, A. H. M. J. Triaud4, and R. G. West8

1  Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK
    e-mail: sjb@astro.keele.ac.uk
2  Centre for Astrophysics & Planetary Science, School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH, UK
3  School of Physics and Astronomy, University of St. Andrews, North Haugh, Fife KY16 9SS, UK
4  Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland
5  Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, Bat. B5C, Liège 1, Belgium
6  Vanderbilt University, Department of Physics and Astronomy, Nashville, TN 37235, USA
7  Astrophysics Research Centre, School of Mathematics & Physics, Queens University, University Road, Belfast BT7 1NN, UK
8  Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK

Received 20 August 2009 / Accepted 1 October 2009

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 HD 186753B has an orbital period of P=1.9194 days, a mass of $M=0.24\pm0.02~M_{\odot}$ and radius of $R=0.31^{+0.06}_{-0.06}~R_{\odot}$; and that TCY7096-222-1B has an orbital period of P=8.9582 days, a mass of between 0.29 and 0.54 $M_{\odot}$ depending on eccentricity and radius of $R=0.263^{+0.02}_{-0.07}~R_{\odot}$. 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.

Key words: binaries: eclipsing -- stars: early-type -- stars: late-type -- stars: individual: HD 186753 -- stars: individual: TCY7096-222-1

© ESO 2009