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arXiv · 2407.21696

GEO and LEO: The Final Frontier for Plutonic FFP Parallax

Andrew Gould
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Abstract

I show that microlens parallaxes, $π_{\rm E}$, can be derived for free-floating planets (FFPs) with masses down to that of Pluto, by combining observations from a satellite in geosynchronous (GEO) orbit with another observatory that is on or near Earth's surface, i.e., either ground-based or in low Earth orbit (LEO). Because these low-mass FFPs typically have measurements of the angular Einstein radius, $θ_{\rm E}$, from finite-source effects, such $π_{\rm E}$ measurements directly yield the FFP mass $M=θ_{\rm E}/κπ_{\rm E}$ where $κ$ is a physical constant. Such Earth-GEO measurements almost perfectly complement Earth-L2 measurements, which extend to higher FFP mass and greater FFP distance. LEO-only observations can yield mass measurement at even smaller FFP mass and nearer FFP distances. I discuss methods for breaking the Refsdal (1966) two-fold degeneracy in $π_{{\rm E},\pm}$.

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Andrew Gould. 2024-07-31. GEO and LEO: The Final Frontier for Plutonic FFP Parallax. https://arxiv.org/abs/2407.21696

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