Astrophys. J., 663, 573-582 (2007/July-1)
The mass and radius of the unseen M dwarf companion in the single-lined eclipsing binary HAT-TR-205-013.
BEATTY T.G., FERNANDEZ J.M., LATHAM D.W., BAKOS G.A., KOVACS G., NOYES R.W., STEFANIK R.P., TORRES G., EVERETT M.E. and HERGENROTHER C.W.
Abstract (from CDS):
We derive masses and radii for both components in the single-lined eclipsing binary HAT-TR-205-013, which consists of an F7 V primary and a late M dwarf secondary. The system's period is short, P=2.230736±0.000010 days, with an orbit indistinguishable from circular, e=0.012±0.021. We demonstrate generally that the surface gravity of the secondary star in a single-lined binary undergoing total eclipses can be derived from characteristics of the light curve and spectroscopic orbit. This constrains the secondary to a unique line in the mass-radius diagram, with M/R2 = constant. For HAT-TR-205-013, we assume the orbit has been tidally circularized and that the primary's rotation has been synchronized and aligned with the orbital axis. Our observed line broadening, Vrotsinirot=28.9±1.0 km/s, gives a primary radius of RA=1.28±0.04 R☉. Our light-curve analysis leads to the radius of the secondary, RB=0.167±0.006 R☉, and the semimajor axis of the orbit, a=7.54±0.30 R☉=0.0351±0.0014 AU. Our single-lined spectroscopic orbit and the semimajor axis then yield the individual masses MB=0.124±0.010 M☉ and MA=1.04±0.13 M☉. Our result for HAT-TR-205-013 B lies above the theoretical mass-radius models from the Lyon group, consistent with results from double-lined eclipsing binaries. The method we describe offers the opportunity to study the very low end of the stellar mass-radius relation.
Stars: Binaries: Eclipsing - Stars: Binaries: Spectroscopic - Stars: Fundamental Parameters - Stars: Low-Mass, Brown Dwarfs - Stars: Rotation
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<Available at CDS (J/ApJ/663/573): table4.dat table5.dat>
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