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Lucas Brefka

Publications and source records attributed to Lucas Brefka.

3 recordsLinked to original sources

Effects of Pebble Accretion Isolation Mass on Observable Exoplanet Properties

The Kepler Mission has discovered a plethora of planetary systems with super-Earth sized planets. These systems exhibit many properties, from widely-spaced planets with non-negligible eccentricities and inclinations, to tightly-spaced, coplanar, and nearly circular multi-planet systems. The observable properties of these systems, such as planet-planet spacings, multiplicity and orbital morphology, can be strongly influenced by the initial conditions of formation. These conditions affect the early growth of planetary embryos in the gas disk phase through pebble and/or planetesimal accretion, which then affects the final growth of planets during the giant impact stage. In this work, we investigate how assumptions of different limiting embryo isolation masses during early stages of planet formation affect the final properties of super-Earth planets within the inner disk, comparing our mock-observed results to each other, as well as to the Kepler sample. We test several models of pebble accretion isolation mass, including pebble isolation, flow isolation, and migration feedback isolation and otherwise adopt the same parameters for the gas disk. We find that while each model can match at least one distribution of observables in the Kepler catalog, they fall short of matching all distributions simultaneously, even with extreme reweighting. Our inability to match all observations suggests that the initial conditions and/or modeled effects in our simulations that we held fixed should be investigated. This exploration sheds light on how planetary systems evolve and the processes that influence the wide range of system parameters we observe today, helping place our own Solar System in context.

astro-ph.EP

Are We There Yet? Challenges in Quantifying the Frequency of Earth Analogs in the Habitable Zone

Searching for life elsewhere in the universe is one of the most highly prioritized pursuits in astronomy today. However, the ability to observe evidence of Earth-like life through biosignatures is limited by the number of planets in the solar neighborhood with conditions similar to Earth. The occurrence rate of Earth-like planets in the habitable zones of Sun-like stars, $\eta_{\oplus}$, is therefore crucial for addressing the apparent lack of consensus on its value in the literature. Here we present a review of the current understanding of $\eta_{\oplus}$. We first provide definitions for parameters that contribute to $\eta_{\oplus}$. Then, we discuss the previous and current estimated parameter values and the context of the limitations on the analyses that produced these estimates. We compile an extensive list of the factors that go into any calculation of $\eta_{\oplus}$, and how detection techniques and surveys differ in their sensitivity and ability to accurately constrain $\eta_{\oplus}$. Understanding and refining the value of $\eta_{\oplus}$ is crucial for upcoming missions and telescopes, such as the planned Habitable Worlds Observatory and the Large Interferometer for Exoplanets, which aim to search for biosignatures on exoplanets in the solar neighborhood.

astro-ph.EP

A General Origin for Multi-Planetary Systems With Significantly Misaligned USP Planets

Ultra-short period (USP) planets are exoplanets which have orbital periods of less than one day and are unique because they orbit inside the nominal magnetic truncation gap of their host stars. In some cases, USP planets have also been observed to exhibit unique dynamical parameters such as significant misalignments in inclination angle with respect to nearby planets. In this paper, we explore how the geometry of a multi-planet system hosting a USP planet can be expected to evolve as a star ages. In particular, we explore the relationship between the mutual inclination of the USP planet and the quadrupole moment ($J_2$) of the host star. We use secular perturbation theory to predict the past evolution of the example TOI-125 system, and then confirm the validity of our results using long-term N-body simulations. Through investigating how the misalignment between the candidate USP planet and the three other short-period planets in the TOI-125 system arose, we intend to derive a better understanding of the population of systems with misaligned USP planets and how their observed parameters can be explained in the context of their dynamical histories.

astro-ph.EP