Radio Activity from the Rapidly Rotating T dwarf 2MASS 2228-4310

We present the detection of 2MASS J22282889-4310262 (2M2228), a T6/T6.5 brown dwarf, using the Karl G. Jansky Very Large Array (VLA) archival data observed at C band (4–8 GHz) over two observing epochs (2 × 96 minutes). 2M2228 is detected at time and frequency averaged Stokes I and V peak flux densities of ${67.3\pm 4.9\ \mu \ \rm {Jy beam}^{-1}}$ and 14.4 ± 3.0 μJybeam−1 in the first epoch and ${107.2\pm 5.2\ \mu \rm {Jy\ beam}^{-1}}$ and −20.7 ± 1.2 μJybeam−1 in the second epoch. This discovery constitutes the eighth and, notably, the most rapidly rotating T dwarf detected to date at radio wavelengths. Our observations reveal highly polarised bursts at fractional polarisation ratios fc > 50%. Using Stokes I light curves, we measure occurrence intervals of ~47 and ~58 minutes in the two observing epochs respectively with the first burst aligning within a half period timescale of the the previously measured mid infrared photometric period of 85.8 ± 0.32 minutes. We attribute the emission to the electron cyclotron maser emission (ECME) and constrain the magnetic field strength to B ≳ 1.4 kG. We emphasise that the periods inferred are provisional considering the short observing durations. The combination of previously demonstrated atmospheric stability and newly detected radio emission in 2M2228 makes it a promising laboratory for testing magnetospheric currents-driven auroral models. Future coordinated James Webb Space Telescope (JWST) and radio observations will further probe the link between auroral activity and atmospheric dynamics in this brown dwarf.