R. K. Barry

Earth as an Extrasolar Planet: Earth Model Validation Using EPOXI Earth Observations

The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institutes Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ∼100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earths lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ∼10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ∼7% and brightness temperature errors of less than 1 K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earths time-dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared. Key Words: Astrobiology-Extrasolar terrestrial planets-Habitability-Planetary science-Radiative transfer. Astrobiology 11, 393-408.

EXOZODIACAL DUST LEVELS FOR NEARBY MAIN-SEQUENCE STARS: A SURVEY WITH THE KECK INTERFEROMETER NULLER

The Keck Interferometer Nuller (KIN) was used to survey 25 nearby main-sequence stars in the mid-infrared, in order to assess the prevalence of warm circumstellar (exozodiacal) dust around nearby solar-type stars. The KIN measures circumstellar emission by spatially blocking the star but transmitting the circumstellar flux in a region typically 0.1-4 AU from the star. We find one significant detection (η Crv), two marginal detections (γ Oph and α Aql), and 22 clear non-detections. Using a model of our own solar systems zodiacal cloud, scaled to the luminosity of each target star, we estimate the equivalent number of target zodis needed to match our observations. Our three zodi detections are η Crv (1250 ± 260), γ Oph (200 ± 80), and α Aql (600 ± 200), where the uncertainties are 1σ. The 22 non-detected targets have an ensemble weighted average consistent with zero, with an average individual uncertainty of 160 zodis (1σ). These measurements represent the best limits to date on exozodi levels for a sample of nearby main-sequence stars. A statistical analysis of the population of 23 stars not previously known to contain circumstellar dust (excluding η Crv and γ Oph) suggests that, if the measurement errors are uncorrelated (for which we provide evidence) and if these 23 stars are representative of a single class with respect to the level of exozodi brightness, the mean exozodi level for the class is <150 zodis (3σ upper limit, corresponding to 99% confidence under the additional assumption that the measurement errors are Gaussian). We also demonstrate that this conclusion is largely independent of the shape and mean level of the (unknown) true underlying exozodi distribution.

Pathway to the Galactic Distribution of Planets: Combined Spitzer and Ground-Based Microlens Parallax Measurements of 21 Single-Lens Events

We present microlens parallax measurements for 21 (apparently) isolated lenses observed toward the Galactic bulge that were imaged simultaneously from Earth and Spitzer, which was ~1 AU west of Earth in projection. We combine these measurements with a kinematic model of the Galaxy to derive distance estimates for each lens, with error bars that are small compared to the Suns galactocentric distance. The ensemble therefore yields a well-defined cumulative distribution of lens distances. In principle, it is possible to compare this distribution against a set of planets detected in the same experiment in order to measure the Galactic distribution of planets. Since these Spitzer observations yielded only one planet, this is not yet possible in practice. However, it will become possible as larger samples are accumulated.

A SEARCH FOR ADDITIONAL PLANETS IN THE NASA EPOXI OBSERVATIONS OF THE EXOPLANET SYSTEM GJ 436

We present time series photometry of the M dwarf transiting exoplanet system GJ?436 obtained with the Extrasolar Planet Observation and Characterization (EPOCh) component of the NASA EPOXI mission. We conduct a search of the high-precision time series for additional planets around GJ?436, which could be revealed either directly through their photometric transits or indirectly through the variations these second planets induce on the transits of the previously known planet. In the case of GJ?436, the presence of a second planet is perhaps indicated by the residual orbital eccentricity of the known hot Neptune companion. We find no candidate transits with significance higher than our detection limit. From Monte Carlo tests of the time series, we rule out transiting planets larger than 1.5 R ? interior to GJ?436b with 95% confidence and larger than 1.25 R ? with 80% confidence. Assuming coplanarity of additional planets with the orbit of GJ?436b, we cannot expect that putative planets with orbital periods longer than about 3.4?days will transit. However, if such a planet were to transit, we would rule out planets larger than 2.0 R ? with orbital periods less than 8.5?days with 95% confidence. We also place dynamical constraints on additional bodies in the GJ?436 system, independent of radial velocity measurements. Our analysis should serve as a useful guide for similar analyses of transiting exoplanets for which radial velocity measurements are not available, such as those discovered by the Kepler mission. From the lack of observed secular perturbations, we set upper limits on the mass of a second planet as small as 10 M ? in coplanar orbits and 1 M ? in non-coplanar orbits close to GJ?436b. We present refined estimates of the system parameters for GJ?436. We find P = 2.64389579 ? 0.00000080 d, R ?= 0.437 ? 0.016 R ?, and Rp = 3.880 ? 0.147 R ?. We also report a sinusoidal modulation in the GJ?436 light curve that we attribute to star spots. This signal is best fit by a period of 9.01?days, although the duration of the EPOCh observations may not have been long enough to resolve the full rotation period of the star.

SYSTEM PARAMETERS, TRANSIT TIMES, AND SECONDARY ECLIPSE CONSTRAINTS OF THE EXOPLANET SYSTEMS HAT-P-4, TrES-2, TrES-3, and WASP-3 FROM THE NASA EPOXI MISSION OF OPPORTUNITY

As part of the NASA EPOXI Mission of Opportunity, we observed seven known transiting extrasolar planet systems in order to construct time series photometry of extremely high phase coverage and precision. Here we present the results for four hot-Jupiter systems with near-solar stars?HAT-P-4, TrES-3, TrES-2, and WASP-3. We observe 10 transits of HAT-P-4, estimating the planet radius Rp = 1.332 ? 0.052 R Jup, the stellar radius R = 1.602 ? 0.061?R ?, the inclination i = 89.67 ? 0.30?deg, and the transit duration from first to fourth contact ? = 255.6 ? 1.9 minutes. For TrES-3, we observe seven transits and find Rp = 1.320 ? 0.057 R Jup, R = 0.817 ? 0.022 R ?, i = 81.99 ? 0.30?deg, and ? = 81.9 ? 1.1 minutes. We also note a long-term variability in the TrES-3 light curve, which may be due to star spots. We observe nine transits of TrES-2 and find Rp = 1.169 ? 0.034 R Jup, R = 0.940 ? 0.026 R ?, i = 84.15 ? 0.16 deg, and ? = 107.3 ? 1.1 minutes. Finally, we observe eight transits of WASP-3, finding Rp = 1.385 ? 0.060 R Jup, R = 1.354 ? 0.056 R ?, i = 84.22 ? 0.81 deg, and ? = 167.3 ? 1.3 minutes. We present refined orbital periods and times of transit for each target. We state 95% confidence upper limits on the secondary eclipse depths in our broadband visible bandpass centered on 650 nm. These limits are 0.073% for HAT-P-4, 0.062% for TrES-3, 0.16% for TrES-2, and 0.11% for WASP-3. We combine the TrES-3 secondary eclipse information with the existing published data and confirm that the atmosphere likely does not have a temperature inversion.

Confirmation of the Planetary Microlensing Signal and Star and Planet Mass Determinations for Event OGLE-2005-BLG-169

We present Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations of the source and lens stars for planetary microlensing event OGLE-2005-BLG-169, which confirm the relative proper motion prediction due to the planetary light curve signal observed for this event. This (and the companion Keck result) provide the first confirmation of a planetary microlensing signal, for which the deviation was only 2%. The follow-up observations determine the flux of the planetary host star in multiple passbands and remove light curve model ambiguity caused by sparse sampling of part of the light curve. This leads to a precise determination of the properties of the OGLE-2005-BLG-169Lb planetary system. Combining the constraints from the microlensing light curve with the photometry and astrometry of the HST/WFC3 data, we find star and planet masses of

The Asymmetric Dust Environment of IK Tauri

{M}_{*}=0.69\pm 0.02{M}_{\odot }

VIEWS FROM EPOXI: COLORS IN OUR SOLAR SYSTEM AS AN ANALOG FOR EXTRASOLAR PLANETS

and

Silicate Dust in the Environment of RS Ophiuchi following the 2006 Eruption

{m}_{{\rm{p}}}=14.1\pm 0.9{M}_{\oplus }

Spitzer Observations of OGLE-2015-BLG-1212 Reveal a New Path toward Breaking Strong Microlens Degeneracies

. The planetary microlens system is located toward the Galactic bulge at a distance of