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See detailSpitzer Transits Of The Super-Earth Gj1214b And Implications For Its Atmosphere
Fraine, Jonathan D.; Deming, D.; Gillon, Michaël ULg et al

in AAS/Division for Planetary Sciences Meeting Abstracts (2012, October 01)

We observed the transiting super-Earth exoplanet GJ1214b using Warm Spitzer at 4.5 μm wavelength during a 20-day quasi-continuous sequence in May 2011. The goals of our long observation were to accurately ... [more ▼]

We observed the transiting super-Earth exoplanet GJ1214b using Warm Spitzer at 4.5 μm wavelength during a 20-day quasi-continuous sequence in May 2011. The goals of our long observation were to accurately define the infrared transit radius of this nearby super-Earth, to search for the secondary eclipse, and to search for other transiting planets in the habitable zone of GJ1214. We here report results from the transit monitoring of GJ1214b, including a re-analysis of previous transit observations by Desert et al. (2011). In total, we analyze 14 transits of GJ1214b at 4.5 μm, 3 transits at 3.6 μm, and 7 new ground-based transits in the I+z band. Our new Spitzer data by themselves eliminate cloudless solar composition atmospheres for GJ1214b, and methane-rich models from Howe & Burrows (2012). Using our new Spitzer measurements to anchor the observed transit radii of GJ1214b at long wavelengths, and adding new measurements in I+z, we evaluate models from Benneke & Seager (2012) and Howe & Burrows (2012) using a χ2 analysis. We find that the best-fit model exhibits an increase in transit radius at short wavelength due to Rayleigh scattering. Pure water atmospheres are also possible. However, a flat line (no atmosphere detected) remains among the best of the statistically acceptable models, and better than pure water atmospheres. We explore the effect of systematic differences among results from different observational groups, and we find that the flat line model is the least sensitive to systematic error. [less ▲]

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See detailImproved precision on the radius of the nearby super-Earth 55 Cnc e
Gillon, Michaël ULg; Demory, B.-O.; Benneke, B. et al

in Astronomy and Astrophysics (2012), 539

We report on new transit photometry for the super-Earth 55 Cnc e obtained with Warm Spitzer/IRAC at 4.5 microns. An individual analysis of these new data leads to a planet radius of 2.21-0.16+0.15 Rearth ... [more ▼]

We report on new transit photometry for the super-Earth 55 Cnc e obtained with Warm Spitzer/IRAC at 4.5 microns. An individual analysis of these new data leads to a planet radius of 2.21-0.16+0.15 Rearth, in good agreement with the values previously derived from the MOST and Spitzer transit discovery data. A global analysis of both Spitzer transit time-series improves the precision on the radius of the planet at 4.5 microns to 2.20+-0.12 Rearth. We also performed an independent analysis of the MOST data, paying particular attention to the influence of the systematic effects of instrumental origin on the derived parameters and errors by including them in a global model instead of performing a preliminary detrending-filtering processing. We deduce from this reanalysis of MOST data an optical planet radius of 2.04+-0.15 Rearth that is consistent with our Spitzer infrared radius. Assuming the achromaticity of the transit depth, we performed a global analysis combining Spitzer and MOST data that results in a planet radius of 2.17+-0.10 Rearth (13,820+-620 km). These results confirm that the most probable composition of 55 Cnc e is an envelope of supercritical water above a rocky nucleus. [less ▲]

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See detailDetection of a transit of the super-Earth 55 Cnc e with Warm Spitzer
Demory, B.-O.; Gillon, Michaël ULg; Deming, D. et al

in Astronomy and Astrophysics (2011), 533

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 ... [more ▼]

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_oplus as measured in IRAC 4.5 μm channel. A planetary mass of 7.81-0.53+0.58 M_oplus is derived from an extensive set of radial-velocity data, yielding a mean planetary density of 4.78-1.20+1.31 g cm-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. [less ▲]

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