X-Ray Coronae from Stars
A number of major advances in stellar coronal physics have occurred since 1990 mainly as a consequence of imaging observations by ROSAT and spectroscopic observations by ASCA. These can be summarised as follows: 1.an all-sky survey has been performed by ROSAT at a sensitivity of ~ 2 × 10−13 erg cm−2 s−1, complemented by pointed observations an order of magnitude deeper;2.complete mapping and deeper pointings have been obtained for virtually all open clusters closer than ~ 500 pc, and covering the age range from ~ 30 Myr to ~ 700 Myr;3.complete mapping and deeper paintings have been obtained for several Star Forming Regions (SFRs) covering the age range ~ 1 to ~ 10 Myr;4.spectroscopic observations of bright coronal sources have been obtained with EUVE and ASCA allowing the derivation of the temperature structure and elemental abundances.