Disks and Exoplanets Projects

Exoplanets Atmospheres: Retrieving Molecular Fingerprints in High Resolution Spectra

The field of exoplanet atmospheric studies is fast developing.
A new, very powerful technique is to analyze the high-resolution spectra of exoplanets.
During observation the light collected by the largest telescopes is passed through a high resolution spectrograph. The resulting optical and near-infrared spectra resolve individual lines of atoms and molecules in the observed exoplanet.

However, the lines of the planet are far too weak to be discerned in the photon noise of their host star. Here the powerful technique of cross-correlation can help.
It shifts a theoretical line mask over the observation, collecting the signal of many individual lines. This method works well, and has been used to detect atoms, ions, and molecules in the past. It also allows to measure wind speeds and spin rates of exoplanets.

In this project the student will create theoretical high resolution spectra with an existing code, and cross-correlate them with mock observations. The question that will be answered is how difficult it is to detect isotopologues (the molecular equivalent of isotopes) in the atmosphere of so-called hot Jupiters. These are gas giant planets in a close-in orbit around their star. The temperatures in their atmospheres can reach a few thousand K.
Carrying out the cross-correlation many times, and assessing the quality of the signal, allows to derive the distribution of parameters describing the atmosphere: temperatures and molecular composition. To find these distributions techniques such as Markov Chain Monte Carlo (MCMC) or Nested Sampling will be used. The goal is to find out how reliably the atmospheric temperature profile can be deduced from the observations, and how well abundance ratios of isotopologues can be constrained.

Interested and motivated students should have experience in programming in Python, as well as using Unix-based operating systems such as Linux. Moreover, basic knowledge of the principles of radiative transfer is desirable.

 
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