ExoExplorer Science Series: Daniel Yahalomi (Columbia) & James Mang (UT Austin)

The ExoExplorer Science Series presents talks by cohort members Daniel Yahalomi (Columbia) & James Mang (UT Austin) on April 12, 2024, from 11 AM - 12 PM Pacific Standard / 2 PM - 3 PM Eastern Standard. Connection information is below.

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Speaker: Daniel Yahalomi (Columbia)

Title: From Wobbles to Worlds: Exploring the Orbital Landscape of Exoplanet TTVs

Abstract: Transit timing variations (TTVs) are ubiquitous in exoplanet transit datasets, with Kepler alone containing ~2,000 periodic TTVs. However, these TTVs are often ambiguous from a model selection perspective, as it is difficult to determine the physical cause of a TTV, be it another planet, a moon, or stellar activity. Currently, careful considerations must be taken, on a case-by-case basis, using computationally expensive N-body simulations, in order to determine the cause of an observed TTV signal. In this talk, we will discuss our work building TTV model selection techniques, through investigations of the orbital landscape of exoplanet TTVs. Specifically, we will focus our discussion on two primary areas: the exomoon corridor and the exoplanet edge. The exomoon corridor ranges from two-to-four times the orbital period of the transiting planet, and is where we expect a pile-up (~50%) of exomoon induced TTVs near the Nyquist period due to aliasing caused by undersampling. We will share our results from searching the exomoon corridor for moon-like TTVs and our follow-up analysis of one of these systems. We will also present our finding that perturbing planets are not expected to induce a TTV with an observed dominant period less than half their own orbital period. This “exoplanet edge” is the manifestation of an observational alias of the true TTV period. The presence of an anomalous dominant TTV period, in a two-planet system, that falls below the exoplanet edge would demonstrate that there exists additional mass in the system, besides the two known exoplanets. Finally, we identify a number of two-planet systems, in Kepler data, that don't lie on the exoplanet edge, and discuss several possible explanations for additional mass in the system.

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Speaker: James Mang (UT Austin)

Title: Modeling Water Clouds in Substellar Atmospheres in the Era of JWST

Abstract: Water must condense into ice clouds in the coldest brown dwarfs and exoplanets. When they form, these icy clouds change the emergent spectra, temperature structure, and albedo of the substellar atmosphere. The properties of clouds are governed by complex microphysics but these complexities are often not captured by the simpler parameterized cloud models used in climate models or retrieval models. To accurately interpret the exquisite details JWST observations show of ultra-cool substellar objects, we need to be prepared to efficiently generate atmospheric models without compromising the accuracy of the cloud’s morphology and optical properties, both of which significantly impact the observables. In this talk, I will discuss how we combine microphysical cloud modeling and 1D climate modeling with the goal of incorporating insights from microphysical models into a self-consistent, parameterized cloud model. I will highlight the differences we see in the observables between the current water cloud prescription and those with our new microphysically informed water clouds. The improvements discussed here will be used towards analyzing JWST observations of ultra-cool substellar worlds including WISE 0855, the coldest known brown dwarf.

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Meeting ID: 895 6518 0020