DENIS 1048-39 and FU Tau A, and their role within the class of X-ray active very low-mass objects | Beate Stelzer ( INAF- Osservatorio Astronomico di Palermo )

Very low-mass stars and brown dwarfs are fully convective, a reason to expect that the solar-like dynamo does not work. Implications for the pattern of magnetic activity are expected. Putting X-ray emission in context with activity signatures in other wavebands (optical and radio) allows to understand the changes — if any — of the coronal heating mechanism across the fully convective boundary and the hydrogen burning mass limit. Young brown dwarfs, moreover, possess circumstellar disks from which they accrete matter. Considering them substellar analogs to T Tauri stars, accretion shocks represent potential sites of X-ray emission next to the coronal plasma. I discuss recent X-ray observations of two brown dwarfs in the context described above: DENIS 1048-39, a very low-mass field star observed in the past to be a radio burst source, and FU Tau A, the primary of an isolated young brown dwarf binary.