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Dynamical Masses and Radii of Eclipsing Giants Discovered by KELT

Published onJun 01, 2020
Dynamical Masses and Radii of Eclipsing Giants Discovered by KELT

Precise stellar masses and radii, inferred from detailed analysis of eclipsing binary systems (EBs), are crucial to our understanding of stellar physics and evolution. While Main Sequence dwarfs have been rather well studied with these techniques, evolved giants have not, largely due to a lack of known suitable eclipsing systems. To date, fewer than 5 giant stars boast masses and radii known to few-percent precision. The few examples known are necessarily not representative of the entire giant star population, limiting our detailed knowledge of stellar evolution up to and during the giant phase. In some binary systems, interaction (e.g., tides or magnetism) between stars causes measured radii to differ from their values in isolation. As a result, non-interacting systems are especially useful for study but often harder to find. Generally, stellar separations must be large compared to radii to avoid interaction. For giants, these wide separations imply long orbital periods of a year or more. Finding events at these time scales requires long-duration photometric time series. This high observational cost is partly responsible for the small number of known systems. The Kilodegree Extremely Little Telescope (KELT) survey for transiting exoplanets has been observing bright stars for over 10 years. Using its long time baseline, we have identified long-period, detached EBs with giant components suitable for detailed characterization. Using a combination of photometric, spectroscopic, and interferometric follow-up data we have begun to characterize these systems in detail in order to extract high-precision stellar parameters of giant stars and their companions, providing important new data points for our understanding of giant star evolution. In this work we provide an overview of the eclipsing systems observed to-date as well as plans for future work.

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