X-ray activity at the low-mass end of the main-sequence

We propose to embark upon a systematic investigation of Xray activity on fieldstars and brown dwarfs at the spectral type M/L transition and beyond usingsensitive XMMNewton observations. The aim of this study is to examine thenature and efficiency of stellar dynamos at the bottom of the mainsequence. Forthis purpose we carefully selected a sample of ultracool dwarfs (spectral typeM7 and later) which are nearby (within 15 pc) and known to sustain achromosphere (Halpha emission has been detected). These characteristics make ourtargets most promising in a search for Xray emission. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]