Dynamic Photometric Variability in Three Young Brown Dwarfs in Taurus: Detection of Optical Flares with TESS Data

Abstract

We present I-band time-series photometric variability studies of three known nearby (∼140 pc) and young (∼1 Myr) brown dwarfs (BD) in the Taurus star-forming region in the Perseus molecular cloud. From 10 nights of observations over a time span of 10 yr, with a typical run of 3–6 hr each night, we estimated that the BDs show unstable short-scale periodicity from 1.5 to 4.8 hr. Using the long-term photometry from the Transiting Exoplanet Survey Satellite (TESS), we have conducted a time-resolved variability analysis of CFHT-BD-Tau 3 and CFHT-BD-Tau 4, revealing orbital periods of ∼0.96 days and ∼3 days respectively, consistent with earlier studies. We also found two superflares in TESS sector 43 data for CFHT-BD-Tau 4 and estimated the flare energies as 7.09 × 10³⁵ erg and 3.75 × 10³⁶ erg. A magnetic field of ∼3.39 kG is required to generate such flare energies on this BD. We performed spot modeling analysis on CFHT-BD-Tau 3 and CFHT-BD-Tau 4 to address the variability detected in the data using the package BASSMAN. Spectral energy distribution and infrared colors of the sources suggest that they have a sufficient amount of circumstellar material around them.