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Aligned and eccentric close-in gas giants: an emerging population and their possible origins

Presentation #401.02 in the session Dynamics, Obliquities, and Tides.

Published onApr 03, 2024
Aligned and eccentric close-in gas giants: an emerging population and their possible origins

Hundreds of close-in gas giants have well-characterized orbits with measured eccentricities and stellar obliquities allowing us to test models of their formation and evolution pathways. However, the large majority are hot Jupiters with orbits that have been nearly circularized and with stellar obliquities that could have been shaped by tides, largely erasing the information about their formation history. In this talk, I will discuss a more pristine and rapidly-growing population of eccentric warm Jupiters and argue that these provide a promising testbed to test our models. I will show our recent Rossiter-Mclaughlin measurements using the ESPRESSO spectrograph of two eccentric (e = 0.4 and e = 0.73) warm Jupiters displaying striking orbital alignment within a couple of degrees of their projected host star’s equators. Added to the current sample, these discoveries suggest that eccentric (e > 0.4) gas giants inside 0.2 au are well-aligned, even more so than their lower eccentricity counterparts. Finally, I will discuss how this unexpected result can rule out various models of high-eccentricity migration that also excite large stellar obliquities (e.g., the von Zeipel-Kozai-Lidov mechanism, planet-planet scattering) and suggest that other mechanisms are at play, including coplanar high-eccentricity migration or eccentricity excitation by disk-planet interactions in disk with inner cavities.

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