Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars

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 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 $T_{\rm EFF}$ scale for solar-like stars, as a function of both spectral type and $(V-K)_0$ color, with an precision of $\bar{\Delta T}_{\rm {(V-K)}_0} = 138$K over the range $(V-K)_0=0.0-4.0$ and $\bar{\Delta T}_{\rm {SpType}} = 105$K for the range F6V -- G5V. Additionally, we provide in an appendix spectral energy distribution fits for the 166 stars with known planets which have sufficient photometry available in the literature for such fits; this derived "{\tt XO-Rad}" database includes homogenous estimates of bolometric flux, reddening, and angular size.Comment: Accepted for publication in Ap

The Spitzer 24μm Photometric Light Curve of the Eclipsing M-dwarf Binary GU Boötis

We present a carefully controlled set of Spitzer 24 μm MIPS time series observations of the low mass eclipsing binary star GU Boötis (GU Boo). Our data cover three secondary eclipses of the system: two consecutive events and an additional eclipse six weeks later. The study’s main purpose is the long wavelength characterization of GU Boo’s light curve, independent of limb darkening and less sensitive to surface features such as spots. Its analysis allows for independent verification of the results of optical studies of GU Boo. Our mid-infrared results show good agreement with previously obtained system parameters. In addition, the analysis of light curves of other objects in the field of view serves to characterize the photometric stability and repeatability of Spitzer’s MIPS-24 at flux densities between approximately 300–2,000μJy. We find that the light curve root mean square about the median level falls into the 1–4% range for flux densities higher than 1 mJy

Kepler Observations of the Three Pre-Launch Exoplanet Candidates: Discover of Two Eclipsing Binaries and a New Exoplanet

Three transiting exoplanet candidate stars were discovered in a ground-based photometric survey prior to the launch of NASA's Kepler mission. Kepler observations of them were obtained during Quarter 1 of the Kepler mission. All three stars are faint by radial velocity follow-up standards, so we have examined these candidates with regard to eliminating false positives and providing high confidence exoplanet selection. We present a first attempt to exclude false positives for this set of faint stars without high-resolution radial velocity analysis. This method of exoplanet confirmation will form a large part of the Kepler mission follow-up for Jupiter-sized exoplanet candidates orbiting faint stars. Using the Kepler light curves and pixel data, as well as medium-resolution reconnaissance spectroscopy and speckle imaging, we find that two of our candidates are binary stars. One consists of a late-F star with an early M companion, while the other is a K0 star plus a late M-dwarf/brown dwarf in a 19 day elliptical orbit. The third candidate (BOKS-1) is an r = 15 G8V star hosting a newly discovered exoplanet with a radius of 1.12 R_(Jupiter) in a 3.9 day orbit

Direct imaging of planet transit events

Exoplanet transit events are attractive targets for the ultrahigh-resolution capabilities afforded by optical interferometers. The intersection of two developments in astronomy enable direct imaging of exoplanet transits: first, improvements in sensitivity and precision of interferometric instrumentation; and second, identification of ever-brighter host stars. Efforts are underway for the first direct high-precision detection of closure phase signatures with the CHARA Array and Navy Precision Optical Interferometer. When successful, these measurements will enable recovery of the transit position angle on the sky, along with characterization of other system parameters, such as stellar radius, planet radius, and other parameters of the transit event. This technique can directly determine the planet\u27s radius independent of any outside observations, and appears able to improve substantially upon other determinations of that radius; it will be possible to extract wavelength dependence of that radius determination, for connection to characterization of planetary atmospheric composition & structure. Additional directly observed parameters - also not dependent on transit photometry or spectroscopy - include impact parameter, transit ingress time, and transit velocity. Copyright © International Astronomical Union 2014

The 55 Cancri Planetary System: Fully Self-Consistent N-body Constraints and a Dynamical Analysis

We present an updated study of the planets known to orbit 55 Cancri A using 1,418 high-precision radial velocity observations from four observatories (Lick, Keck, Hobby-Eberly Telescope, Harlan J. Smith Telescope) and transit time/durations for the inner-most planet, 55 Cancri "e" (Winn et al. 2011). We provide the first posterior sample for the masses and orbital parameters based on self-consistent n-body orbital solutions for the 55 Cancri planets, all of which are dynamically stable (for at least $10^8$ years). We apply a GPU version of Radial velocity Using N-body Differential evolution Markov Chain Monte Carlo (RUN DMC; B. Nelson et al. 2014) to perform a Bayesian analysis of the radial velocity and transit observations. Each of the planets in this remarkable system has unique characteristics. Our investigation of high-cadence radial velocities and priors based on space-based photometry yields an updated mass estimate for planet "e" ($8.09\pm0.26$ M$_\oplus$), which affects its density ($5.51\pm^{1.32}_{1.00}$ g cm$^{-3}$) and inferred bulk composition. Dynamical stability dictates that the orbital plane of planet "e" must be aligned to within $60^o$ of the orbital plane of the outer planets (which we assume to be coplanar). The mutual interactions between the planets "b" and "c" may develop an apsidal lock about $180^o$. We find 36-45% of all our model systems librate about the anti-aligned configuration with an amplitude of $51^o\pm^{6^o}_{10^o}$. Other cases showed short-term perturbations in the libration of $\varpi_b-\varpi_c$, circulation, and nodding, but we find the planets are not in a 3:1 mean-motion resonance. A revised orbital period and eccentricity for planet "d" pushes it further toward the closest known Jupiter analog in the exoplanet population.Comment: 12 pages, 5 figures, 4 tables, accepted to MNRAS. Figure 2 (left) is updated from published version. Posterior samples available at http://www.personal.psu.edu/ben125/Downloads.htm