Date:June 16, 2023
The ExoExplorer Science Series presents talks by cohort members Jack Lubin (UC Irvine) & Isabella Trierweiler (UCLA) on June 16, 2023, from 11 AM - 12 PM Pacific / 2 PM - 3 PM Eastern. Connection information is below.
Speaker: Jack Lubin (UC Irvine)
Title: Exploring New Dimensions through Time/Frequency Analysis of RV Datasets with Lia
Abstract: One of the most pressing challenges in the new era of Extreme Precision Radial Velocity (EPRV) instruments is to disentangle signals induced by stellar activity from planetary signals. With small exception, planetary signals are distinct from activity signals in that they have a constant frequency, phase, and amplitude. Meanwhile, activity signals may come and go, growing and decaying over a characteristic lifetime, and returning again with possible phase and frequency shifts. Here, we present an approach exploiting this feature: we decompose the RV signal on a basis of apodized sinusoidal functions. Bayesian methods are precise and interpretable but computationally expensive. Periodograms are fast and provide statistics, but are prone to aliasing because they search one signal at a time. Here, we introduce the L1 Apodized Periodogram, L1A or Lia (pronounced like the name, “Leah”). This new software uses an L1 minimization approach, allowing to search for several signals at the same time with a moderate computational cost, to identify and characterize both the periodicity and decay lifetime of signals in a dataset. With a new way to look into our RV data sets, we can gain new insights and better understand the astrophysical origin of signals.
Speaker: Isabella Trierweiler (UCLA)
Title: Mapping exoplanet compositions using polluted white dwarfs
Abstract: A persistent question in exoplanet characterization is whether exoplanetary systems form from similar compositional building blocks to our own. Polluted white dwarf stars offer a unique way to address this question as they provide measurements of the bulk compositions of exoplanetary material. These stars show evidence of recent accretion of rocky bodies in the form of metal lines in their spectra, which tell us about the relative elemental abundances of the accreted material. In this talk I will share a statistical analysis of the rocks polluting white dwarfs and compare their compositions to Solar System rocks, such as chondrites, bulk Earth, and crust. In this study, I find that the majority of the extrasolar rocks are consistent with the composition of chondrites, a result that is supported by the compositions of stars in the solar neighborhood.
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