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Register a new userToward Eclipse Mapping of Hot Jupiters
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Recent Spitzer infrared measurements of hot Jupiter eclipses suggest that eclipse mapping techniques could be used to spatially resolve the day-side photospheric emission of these planets using partial occultations. As a first step in this direction, we simulate ingress/egress lightcurves for the three brightest known eclipsing hot Jupiters and evaluate the degree to which parameterized photospheric emission models can be distinguished from each other with repeated, noisy eclipse measurements. We find that the photometric accuracy of Spitzer is insufficient to use this tool effectively. On the other hand, the level of photospheric details that could be probed with a few JWST eclipse measurements could greatly inform hot Jupiter atmospheric modeling efforts. A JWST program focused on non-parametric eclipse map
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We present the results of recent observations of phase-dependent variations in brightness designed to characterize the atmospheres of hot Jupiters. In particular, we focus on recent observations of the transiting planet HD 189733b at 8 micron using the Spitzer Space Telescope, which allow us to determine the efficiency of the day-night circulation on this planet and estimate the longitudinal positions of hot and cold regions in the atmosphere. We discuss the implications of these observations in the context of two other successful detections of more sparsely-sampled phase variations for the non-transiting systems upsilon And b and HD 179949b, which imply a potential diversity in the properties of the atmospheres of hot Jupiters. Lastly, we highlight several upcoming Spitzer observations that will extend this sample to additional wavelengths and more transiting systems in the near future.
We present near infrared high-precision photometry for eight transiting hot Jupiters observed during their predicted secondary eclipses. Our observations were carried out using the staring mode of the WIRCam instrument on the Canada-France-Hawaii Telescope (CFHT). We present the observing strategies and data reduction methods which delivered time series photometry with statistical photometric precisionas low as 0.11%. We performed a Bayesian analysis to model the eclipse parameters and systematics simultaneously. The measured planet-to-star flux ratios allowed us to constrain the thermal emission from the day side of these hot Jupiters, as we derived the planet brightness temperatures. Our results combined with previously observed eclipses reveal an excess in the brightness temperatures relative to the blackbody prediction for the equilibrium temperatures of the planets for a wide range of heat redistribution factors. We find a trend that this excess appears to be larger for planets with lower equilibrium temperatures. This may imply some additional sources of radiation, such as reflected light from the host star and/or thermal emission from residual internal heat from the formation of the planet.
Here we present the analysis of multi-epoch secondary eclipse observations of HD 189733b and HD 209458b as a probe of temporal variability in the planetary climate using both Spitzer channels 1 and 2 (3.6 and 4.5 um). Constraining temporal variability will inform models and identify physical processes occurring at either length scales too small to directly observe or at pressure levels that are inaccessible to transit observations. We do not detect statistically significant variability and are able to place useful upper limits on the IR variability amplitudes in these atmospheres. There are very few planets with multi-epoch observations at the required precision to probe variability in dayside emission. The observations considered in this study span several years, providing insight into temporal variability at multiple timescales. In the case of HD 189733b, the best fit eclipse depths for the channel 2 observations exhibit a scatter of 102 ppm about a median depth of 1827 ppm and in channel 1 exhibit a scatter of 88 ppm about a median depth of 1481 ppm. For HD 209458b, the best fit eclipse depths for the channel 2 observations exhibit a scatter of 22 ppm about a median depth of 1406 ppm and in channel 1 exhibit a scatter of 131 ppm about a median depth of 1092 ppm. The precision and scatter in these observations allow us to constrain variability to less than (5.6% and 6.0%) and (12% and 1.6%) for channels (1,2) of HD 189733b and HD 209458b respectively. There is a difference in the best fit eclipse timing compared to the predicted time consistent with an offset hotspot as predicted by GCMs and confirmed in previous phase curve observations.
The observed low densities of gas giant planets with a high equilibrium temperature can be simulated in models when a fraction of the surface radiation is deposited deeper in the interior. Meanwhile migration theories suggest that hot Jupiters formed further away from their host-star and migrated inward. We incorporate disk migration in simulations of the evolving interior of hot Jupiters to determine whether migration has a long lasting effect on the inflation of planets. We quantify the difference between the radius of a migrated planet and the radius of a planet that formed in situ as the radius discrepancy. We remain agnostic about the physical mechanism behind interior heating, but assume it scales with the received stellar flux by a certain fraction. We find that the change in irradiation received from the host-star while the planet is migrating can affect the inflation and final radius of the planet. Models with a high fraction of energy deposited in the interior ( > 5%) show a significant radius discrepancy when the deposit is at higher pressures than P=1 bar. For a smaller fraction of 1%, there is no radius discrepancy for any deposit depth. We show that a uniform heating mechanism can cause different rates of inflation, depending on the migration history. If the forthcoming observations on mean densities and atmospheres of gas giants give a better indication of a potential heating mechanism, this could help to constrain the prior migration of such planets.
Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter-McLauglin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blue-shifted) or receding (red-shifted) parts of the planet causes a temporal distortion in the planets spectral line profiles resulting in an anomaly in the planets radial velocity curve. We demonstrate that the shape and the ratio of the ingress-to-egress radial velocity amplitudes depends on the planetary rotational rate, axial tilt and impact factor (i.e. sky-projected planet spin-orbital alignment). In addition, line asymmetries originating from different layers in the atmosphere of the planet could provide information regarding zonal atmospheric winds and constraints on the hot spot shape for giant irradiated exoplanets. The effect is expected to be most-pronounced at near-infrared wavelengths, where the planet-to-star contrasts are large. We create synthetic near-infrared, high-dispersion spectroscopic data and demonstrate how the sky-projected spin axis orientation and equatorial velocity of the planet can be estimated. We conclude that the RMse effect could be a powerful method to measure exoplanet spins.
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