Multi-Wavelength Observations and Modeling of Magnetic Fields in Ultracool Dwarfs and Giant Exoplanets

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The stars with the lowest mass and lowest temperature, called Ultra-Cool Dwarfs (UCDs), are also the most numerous. With fully convective interiors, they historically were thought not to have dynamo-generated magnetic fields. Recent observations have shown that these stars do indeed have magnetic activity. This work will characterize the nature of this magnetic activity, and lead to an understanding of the dynamo responsible for magnetic fields in these stars. Understanding these dynamos will shine light on the workings of the largest exoplanets. The project will engage post-doctoral scholars and undergraduate students. In addition, the work will be incorporated into undergraduate education through the active participation of students in using Harvard-Smithsonian telescopes. The results of the project will be disseminated to the public through talks in the Harvard-Smithsonian Observatory Night program as well as through on-going outreach in popular publications.The team will examine archival data from the VLA and from ALMA, as well as the Pan-STARRS Medium Deep Survey (PS1/MDS) to understand magnetic fields from a variety of ultra-cool dwarf (UCD) stars. They will study (i) the distribution of magnetic field strengths; (ii) the physical scale, topology, and coherence timescale of the magnetic fields; (iii) the ubiquity of dynamos across the full range of UCDs, as well as for the first time in giant exoplanets; and (iv) the rates and energetics of flaring activity in about 100,000 UCDs in the PS1/MDS on timescales of minutes to years, with implications for habitability around UCDs. The results will inform studies with future radio facilities (e.g., Square Kilometer Array) and optical surveys (e.g., the Legacy Survey of Space and Time with NSF’s Vera Rubin Observatory).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.