Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars

Abstract

We present interferometric angular sizes for 12 stars with known planetary companions, for comparison with 28 additional main-sequence stars not known to host planets. For all objects we estimate bolometric fluxes and reddenings through spectral-energy distribution (SED) fits, and in conjunction with the angular sizes, measurements of effective temperature. The angular sizes of these stars are sufficiently small that the fundamental resolution limits of our primary instrument, the Palomar Testbed Interferometer, are investigated at the sub-milliarcsecond level and empirically established based upon known performance limits. We demonstrate that the effective temperature scale as a function of dereddened (V − K)_0 color is statistically identical for stars with and without planets. A useful byproduct of this investigation is a direct calibration of the T_(EFF) scale for solarlike stars, as a function of both spectral type and (V − K)_0 color, with an precision of ΔTbar_((V−K)0) = 138 K over the range (V − K)_0 = 0.0–4.0 and ΔTbar_(SpType) = 105 K for the range F6V–G5V. Additionally, in an Appendix we provide SED fits for the 166 stars with known planets which have sufficient photometry available in the literature for such fits; this derived “XO-Rad” database includes homogeneous estimates of bolometric flux, reddening, and angular size.