Prospects of future X-ray missions for low mass stars and cluster stars

The new generation of X-ray missions to be launched by the end of this century will provide excellent opportunities for the study of very-low mass stars and brown dwarfs as well as of cool stars in open clusters and star forming regions. AXAF and XMM will be highly complementary in this respect, with AXAF leading the field for the detection of very faint objects and the study of crowded regions, and XMM allowing medium to high resolution spectroscopy to fainter limits for a large number of stars in open clusters and nearby star forming regions. With the help of simulations of AXAF and XMM spectra, and estimates of the sensitivity limits for typical imaging and spectroscopic observations, I discuss the prospects offered by these two missions for the study of low-mass stars and cluster stars.