Observational Studies of Magnetic Fields in Very Low Mass Stars

Harvard University, Cambridge MA

Investigators

Abstract

This is an observational study of the magnetic fields of the smallest stars. These stars have such low temperature and low mass that they are called ultracool dwarfs (UCDs). UCDs are the most common type of star in the Galaxy and they have a surprising amount of magnetic activity that is not understood. This project will address several fundamental questions about UCDs, including how strong are their magnetic fields, how are they distributed around the star, and how do they change over time. Results from this project will also be helpful for studies of the magnetic fields of giant planets around other stars. Undergraduate and graduate students will be trained and mentored in research. They will participate in all stages of the work, including collecting, analyzing, and publishing data at many different wavelengths. The project will also integrate research experiences into undergraduate education and public lectures. This project will exploit a unique set of magnetic activity observations from radio wavelengths to X-rays. The group will measure magnetic field strengths, spectral energy distributions, and time monitoring using radio observations with the Jansky Very Large Array (JVLA) and ALMA telescopes. They will document and analyze UCD flares and variability with optical observations using the Pan-STARRS Medium-Deep survey. The role of rotation in convective dynamos will also be studied with X-ray observations that the team obtained from the Chandra telescope. This project will determine the fundamental properties of convective magnetic dynamos, and the resulting range of magnetic activity timescales and energetics. The observations will provide empirical inputs for analytical models and numerical simulations of convective magnetic dynamos. In addition, the study of flares and variability in a million UCD stars on timescales of minutes to years will impact the question of life and habitability in the compact habitable zones of M dwarfs, a popular target population for Earth-like exoplanet searches.