Menu My thesis in 400 words: Anne Boucher

Posted on July 5, 2022 by Erika Le Bourdais

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Anne Boucher, an iREx student at the University of Montreal, presented her doctoral dissertation in late 2021. Here she summarizes the research project she carried out as part of her doctorate.

During my PhD, I became interested in the atmosphere of gas giant exoplanets (as large as Jupiter or Saturn) orbiting very close to their star. Thanks to a technique called transmission spectroscopy, I studied the chemical composition of its atmosphere, which gives a lot of information about its mechanisms of formation and evolution. The detailed study of these exoplanets, which we sometimes call hot jupiters or hot saturns, provides a better understanding of the physical, chemical, and dynamic processes that govern the atmosphere of these astronomical objects.

These are the data from the SPIRou instrument, a high-resolution spectropolarimeter that works in the near infrared and installed in the Canada-France-Hawaii telescope, which I mainly used. We first observed HD189733b, one of the most studied exoplanets, to construct the analysis codes. By exploiting traffic spectroscopy, we were able to confirm the presence of water and determine its abundance. The results obtained, according to previous studies, indicate that the atmosphere of HD 189733 b is relatively clear (no clouds) and that the planet would have formed far from its star, where it is cold enough to find water in shape. of gel. A strong shift towards blue of water absorption was observed, a consequence of the dynamics and winds present in the atmosphere.

Artistic representation of the exoplanet HD 189733 b, credit: NASA, ESA and G. Bacon (STScI)

We then studied WASP-127b, a less massive exoplanet, but much larger than Saturn. A recent study of data from the Hubble Space Telescopes (HST) and Spitzer could not differentiate between two atmospheric scenarios: a low carbon-oxygen (C / O) ratio with low carbon monoxide (CO) or a high proportion and a very high of CO (this relationship can be linked to different training scenarios). SPIRou, which allows to observe a band of CO not accessible to HST and Spitzer, was able to determine that there was very little CO and a very low C / O, which has rarely been observed, but which is supported by a few more. realistic training scenarios that vary over time. SPIRou data also confirmed the presence of water and suggest that, if confirmed, there could even be hydroxyl (OH), an unexpected detection as the exoplanet is too cold. I demonstrated that the joint analysis of SPIRou data and that of space telescopes allows for better limitations on atmospheric parameters.

This work has shown that high-resolution near-infrared transit spectroscopy, especially with SPIRou, is useful for exploring the atmospheric conditions of Jupiters and hot subsaturns. In addition, the combination of low and high resolution data is a very powerful tool for the study of atmospheres and will be even more so with the revolutionary capabilities of JWST.

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Anne worked on her doctorate. graduated from the University of Montreal between 2016 and 2022, under the supervision of David Lafrenière. His thesis will be available soon.


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