UR: Characterizing the atmosphere of hot Jupiter CoRoT-1 b

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Kayli Glidic

University of Arizona

Photo of guest author Kayli Glidic

This guest post was written by Kayli Glidic. Kayli is an undergraduate in her junior year at the University of Arizona, where she is studying astronomy and astrophysics. She conducted this research under the supervision of her advisor, Dr. Everett Schlawin, and presented it at AAS 237.

Despite the inability to spatially resolve exoplanets from their host stars, exoplanetary atmospheres contain a wealth of information that has subsequently placed priority on the spectroscopic analysis of atmospheres and the development of interpretive tools. Probing these environments has returned measurements on both the chemical composition and the thermal structure of these atmospheres that are capable of constraining planetary formation, evolution, and climate. Hot Jupiters present good test cases as they are large, hot, and relatively easily detectable. In particular, exoplanet CoRoT-1 b is especially interesting, as it is predicted to be a transitional planet between hot Jupiters (equilibrium temperatures around 1500K) and ultra-hot Jupiters (equilibrium temperatures over 2000K). Typical hot Jupiters atmospheres are expected to have temperatures that decrease with altitude (non-inverted temperature-pressure profiles) while ultra-hot Jupiters are thought to exhibit different atmospheric properties and may have inverted temperature-pressure profiles.

The spectroscopic data collected on CoRoT-1 b was reduced utilizing a spectroscopic data-reduction pipeline, called the Time Series Helper & Integration Reduction Tool (tshirt), which is a general-purpose tool for time series science. In time-resolved observations, especially for near-infrared detectors, the “ramp effect” is a dominant source of systematics, suggested to be caused by charge trapping, that limits photometric precision. It appears in time-series data as a hook-like feature at the beginning of the observation. Unique to this work was the focused use of the Ramp Effect Charge Trapping Eliminator (RECTE), a tool that takes into account the numbers of charge carrier traps, the trapping efficiency, and the trap lifetimes in every pixel on the detector enabling a better constraint and optimization of the secondary eclipse spectra to compare with representative models in this transitionary temperature regime.

According to our findings, the average secondary eclipse spectra for CoRoT-1 b, as seen in Figure 1, appears to be generally featureless, similar to a blackbody-like emission. This average spectrum, according to CHIMERA models, corresponds best with no heat redistribution and an inverted temperature profile, as seen in Figure 1, indicating a possible upper high altitude layer that strongly absorbs stellar irradiance.

The top plot shows the planet-to-star flux ratio in parts per million from 0 to 6000 against the wavelength from around 1 to 5 µm. Plotted on this are three theoretical models with different amounts of heat distribution from 1.0 (full redistribution) to 2.66 (no heat distribution) which diverge to a wider range of flux ratios at longer wavelengths. Laid over the models are eclipse spectra processed by the author as well as the two data points from Spitzer. The author's spectra overlap most with a redistribution value of 2.66, though with some overlap with value 2.0. The Spitzer data point at 3.6 µm overlaps with a redistribution value of 2.0 while the value at 4.5 µm sits between the redistribution values of 1.0 and 2.0. The bottom plot shows the theoretical temperature-pressure profiles for the three different redistribution values, which range between temperatures from 1600 to 3500 K between pressures 10^-6 to 100 bar. Redistribution values 2.0 and 2.66 follow almost parallel temperature-pressure profiles, with 2.0 at slightly lower temperatures for a given pressure. Redistribution value 1.0 starts parallel to the others at 100 bar, at only slightly lower temperatures. However when the pressure reaches around 0.1 bar, it diverges, slightly decreasing in temperature where the others increase reasonably quickly. It then sharply increases at a pressure of around 10^-4 before flattening off.
Figure 1: On the top plot is the theoretical secondary eclipse CHIMERA model of CoRoT-1 b for three different heat redistributions. Overlaid on top is our average secondary eclipse spectra as well as the two Spitzer wavelengths (3.6 and 4.5 µm). On the bottom plot is plot is the theoretical temperature-pressure profile CHIMERA model of CoRoT-1 b for three different heat redistributions. In red, CoRoT-1 b Redist 1.0, refers to full redistribution (day and night sides have the same temperature-pressure profiles). In purple, CoRoT-1 b Redist 2.0 refers to radiation on the day side only. In blue, CoRoT-1 b Redist 2.66 refers to a “max” (no heat redistribution, almost like a hot spot). 

Astrobite edited by: Ali Crisp
Featured Image Credit: NASA/ESA/G. Bacon

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