Using the brown dwarfs TVLM as examples, two possibilities of the origin of stationary X-ray radiation from ultracool stars have been investigated: (i) radiation from hot corona as a whole and (ii) radiation from a set of magnetic loops with a dense hot plasma heated due to the dissipation of electric currents. It is shown that, for the brown dwarfs under consideration, the generation of X-rays by a set of hot loops is energetically more favourable than in the case of a hot corona.

No abstract

No abstract