Radio activity from the rapidly rotating T dwarf 2MASS 2228-4310

Journal article

We present the detection of 2MASS J22282889−4310262 (2M2228), a T6/T6.5 brown dwarf, using the Karl G. Jansky Very Large Array archival data observed at C band (4–8 GHz) over two observing epochs ( min). 2M2228 is detected at time and frequency averaged Stokes I and V peak flux densities of and in the first epoch and and 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 polarized bursts at fractional polarization ratios per cent. Using Stokes I light curves, we measure occurrence intervals of and min in the two observing epochs, respectively, with the first burst aligning within a half-period time-scale of the the previously measured mid-infrared photometric period of min. We attribute the emission to the electron cyclotron maser emission and constrain the magnetic field strength to kG. We emphasize 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 and radio observations will further probe the link between auroral activity and atmospheric dynamics in this brown dwarf.

Authors: Wandia, K; Garrett, MA; Golden, A; Hallinan, G; Williams-Baldwin, D

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 546
• Issue: 4
• Pages: stag085
• Article number: stag085
• Publication date: 2026-01-20
• Acceptance date: 2026-01-06
• DOI: 10.1093/mnras/stag085
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: stars: magnetic field; radio continuum: stars; stars: brown dwarfs