Patricio Cubillos

Detection of a transit of the super-Earth 55 Cancri e with warm Spitzer

We report on the detection of a transit of the super-Earth 55 Cnc e with warm Spitzer in IRAC’s 4.5 μm band. Our MCMC analysis includes an extensive modeling of the systematic effects affecting warm Spitzer photometry, and yields a transit depth of 410±63 ppm, which translates to a planetary radius of 2.08 +0.16 −0.17 R⊕ as measured in IRAC 4.5 μm channel. A planetary mass of 7.81 +0.58 −0.53 M⊕ is derived from an extensive set of radial-velocity data, yielding a mean planetary density of 4.78 +1.31 −1.20 gc m −3 . Thanks to the brightness of its host star (V = 6, K = 4), 55 Cnc e is a unique target for the thorough characterization of a super-Earth orbiting around a solar-type star.

SPITZER SECONDARY ECLIPSES OF WASP-18b

The transiting exoplanet WASP-18b was discovered in 2008 by the Wide Angle Search for Planets project. The Spitzer Exoplanet Target of Opportunity Program observed secondary eclipses of WASP-18b using Spitzers Infrared Array Camera in the 3.6 ?m and 5.8 ?m bands on 2008 December 20, and in the 4.5 ?m and 8.0 ?m bands on 2008 December 24. We report eclipse depths of 0.30% ? 0.02%, 0.39% ? 0.02%, 0.37% ? 0.03%, 0.41% ? 0.02%, and brightness temperatures of 3100 ? 90, 3310 ? 130, 3080 ? 140, and 3120 ? 110?K in order of increasing wavelength. WASP-18b is one of the hottest planets yet discovered?as hot as an M-class star. The planets pressure-temperature profile most likely features a thermal inversion. The observations also require WASP-18b to have near-zero albedo and almost no redistribution of energy from the day side to the night side of the planet.

Spitzer Observations of the Thermal Emission from WASP-43b

WASP-43b is one of the closest-orbiting hot Jupiters, with a semimajor axis of a?= 0.01526?? 0.00018?AU and a period of only 0.81?days. However, it orbits one of the coolest stars with a hot Jupiter (T *?= 4520?? 120?K), giving the planet a modest equilibrium temperature of T eq?= 1440?? 40?K, assuming zero Bond albedo and uniform planetary energy redistribution. The eclipse depths and brightness temperatures from our jointly fit model are 0.347%?? 0.013% and 1670?? 23?K at 3.6 ?m and 0.382%?? 0.015% and 1514?? 25?K at 4.5 ?m. The eclipse timings improved the estimate of the orbital period, P, by a factor of three (P = 0.81347436 ? 1.4 ? 10?7 days) and put an upper limit on the eccentricity (). We use our Spitzer eclipse depths along with four previously reported ground-based photometric observations in the near-infrared to constrain the atmospheric properties of WASP-43b. The data rule out a strong thermal inversion in the dayside atmosphere of WASP-43b. Model atmospheres with no thermal inversions and fiducial oxygen-rich compositions are able to explain all the available data. However, a wide range of metallicities and C/O ratios can explain the data. The data suggest low day-night energy redistribution in the planet, consistent with previous studies, with a nominal upper limit of about 35% for the fraction of energy incident on the dayside that is redistributed to the nightside.

Thermal Emission of WASP-14b Revealed with Three Spitzer Eclipses

Exoplanet WASP-14b is a highly irradiated, transiting hot Jupiter. Joshi et al. calculate an equilibrium temperature (T eq) of 1866 K for zero albedo and reemission from the entire planet, a mass of 7.3 ± 0.5 Jupiter masses (M J), and a radius of 1.28 ± 0.08 Jupiter radii (R J). Its mean density of 4.6 g cm-3 is one of the highest known for planets with periods less than three days. We obtained three secondary eclipse light curves with the Spitzer Space Telescope. The eclipse depths from the best jointly fit model are 0.224% ± 0.018% at 4.5 μm and 0.181% ± 0.022% at 8.0 μm. The corresponding brightness temperatures are 2212 ± 94 K and 1590 ± 116 K. A slight ambiguity between systematic models suggests a conservative 3.6 μm eclipse depth of 0.19% ± 0.01% and brightness temperature of 2242 ± 55 K. Although extremely irradiated, WASP-14b does not show any distinct evidence of a thermal inversion. In addition, the present data nominally favor models with day-night energy redistribution less than ~30%. The current data are generally consistent with oxygen-rich as well as carbon-rich compositions, although an oxygen-rich composition provides a marginally better fit. We confirm a significant eccentricity of e = 0.087 ± 0.002 and refine other orbital parameters.

ON CORRELATED-NOISE ANALYSES APPLIED TO EXOPLANET LIGHT CURVES

Time-correlated noise is a significant source of uncertainty when modeling exoplanet light-curve data. A correct assessment of correlated noise is fundamental to determine the true statistical significance of our findings. Here we review three of the most widely used correlated-noise estimators in the exoplanet field, the time-averaging, residual-permutation, and wavelet-likelihood methods. We argue that the residual-permutation method is unsound in estimating the uncertainty of parameter estimates. We thus recommend to refrain from this method altogether. We characterize the behavior of the time averagings rms-vs.-bin-size curves at bin sizes similar to the total observation duration, which may lead to underestimated uncertainties. For the wavelet-likelihood method, we note errors in the published equations and provide a list of corrections. We further assess the performance of these techniques by injecting and retrieving eclipse signals into synthetic and real Spitzer light curves, analyzing the results in terms of the relative-accuracy and coverage-fraction statistics. Both the time-averaging and wavelet-likelihood methods significantly improve the estimate of the eclipse depth over a white-noise analysis (a Markov-chain Monte Carlo exploration assuming uncorrelated noise). However, the corrections are not perfect, when retrieving the eclipse depth from Spitzer datasets, these methods covered the true (injected) depth within the 68\% credible region in only

High-resolution spectroscopic search for the thermal emission of the extrasolar planet HD 217107 b

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Secondary Eclipses of HAT-P-13b

45--65\% of the trials. Lastly, we present our open-source model-fitting tool, Multi-Core Markov-Chain Monte Carlo ({MC

CHARACTERIZING EXOPLANETS IN THE VISIBLE AND INFRARED: A SPECTROMETER CONCEPT FOR THE EChO SPACE MISSION

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Young planets under extreme UV irradiation. I. Upper atmosphere modelling of the young exoplanet K2-33b

}). This package uses Bayesian statistics to estimate the best-fitting values and the credible regions for the parameters for a (user-provided) model. {MC

PyTranSpot: A tool for multiband light curve modeling of planetary transits and stellar spots

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