Too Cool for Stellar Rules: A Bayesian Exploration of Trends in Ultracool Magnetism

Ultracool dwarfs are objects in the red and brown dwarf regimes with electrically neutral atmospheres caused by their cool temperatures. To better constrain their magnetic behavior, we use a sample of 196 ultracool dwarfs observed in the 4.5-8.5 GHz range on the Karl G. Jansky Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA). We take a Bayesian approach in analyzing this sample to understand trends in radio luminosity as a function of several fundamental parameters: spectral type, effective temperature, and rotation rate. This sample is composed of mostly null detections, along with a number of confirmed detections, and has both large uncertainties and intrinsic scatter. This is the first rigorous Bayesian analysis applied to radio emissions in the ultracool dwarf regime incorporating the many null detections available. We report the early results indicating decreasing trends in each parameter space.