Magnetic Activity in the Lowest Mass Pre-main Sequence Stars

The spectral type boundary that determines which very lowmass objects willeventually become M stars, vs. brown dwarfs, remains poorly constrained duringpremain sequence evolution. Xray observations of premain sequence M starsoffer a means to probe internal and surface stellar magnetic activity, so as tohelp determine this boundary. However, even though a majority of stars in thesolar neighborhood are of mid to lateM type, the Xray activity of such starsremain essentially unexplored for the important age range 10100 Myr. We proposeto use XMMNewton to observe 14 nearby (Dvirgul50 pc), young (age 1040 Myr) stars oftype M3M6, to investigate the potential decrease in Xray luminosity for verylowmass stars at this age. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]