Gem accommodates gas at a wide range of temperatures. The cooler plasma may be associated with quiet regions and is relatively stable. A hotter component, in the range of about 10 MK, originates from active regions and is rather variable. A very hot component may be present, probably associated with magnetic field disruptions.
Using all available ROSAT observations of Gem one has obtained some information on possible temporal variations in the X-ray emission. The component associated with active regions shows variations on the scale of one year, which may be linked with long term (cyclic) variations of activity. Rotational modulation (19.6 days) has not been detected, but more observations are needed to establish the possible absence of such variations. For the first time sufficient observations have been obtained to demonstrate variations on time scales ranging from hours to minutes. Such variations are to be expected when the highly active character of Gem is taken into account, and is in accordance with results from radio observations of RSCVn systems.
The observations give some support to a model in which quiet region plasma (loops) have temperature around 2 MK. In active regions magnetic field reconnection occurs at large heights and high temperature (40 MK) accelerating oppositely directed particle streams (jets). The downward directed particles impinge on underlying closed loops, create shocks and heat the loops to temperatures around some 10 MK. The structure of the active region corona of Gem may have some properties in common with the model proposed by Shibata et al. (1995) in order to explain compact-loop solar flares.
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998