On the temperature-emission measure distribution in stellar coronae

Strong peaks in the emission measure-temperature ( EM-T) distributions in the coronae of some binary stars are associated with the presence of hot ( 10(7) K), dense ( up to 10(13) cm(-3)) plasma. These peaks are very reminiscent of those predicted to arise in an impulsively heated solar corona. A coronal model comprised of many impulsively heated strands is adapted to stellar parameters. It is shown that the properties of the EM-T distribution can be accounted for in general terms provided the emission comes from many very small loops ( length under 103 km) with intense magnetic fields ( 1 kG) distributed across part of the surface of the star. The heating requires events that generally dissipate between 10(26) and 10(28) ergs, which is in the range of solar microflares. This implies that such stars must be capable of generating regions of localized intense magnetic fields.