GODDARD HIGH-RESOLUTION SPECTROGRAPH OBSERVATIONS OF PROCYON AND HR-1099

Goddard High Resolution Spectrograph (GHRS) observations have revealed the presence of broad wings in the transition-region lines of AU Mic and Capella. It has been proposed that these wings are signatures of m icroflares in the transition regions of these stars and that the solar analog for this phenomenon might be the ''transition region explosive events'' discussed by Dere, Bartoe, & Brueckner. We have analyzed GHR S observations of Procyon (F5 IV-V) and HR 1099 (K1 IV + G5 IV) to sea rch for broad wings in the UV emission lines of these stars. We find t hat the transition-region lines of HR 1099, which are emitted almost e ntirely by the K1 star, do indeed have broad wings that are even more prominent than those of AU Mic and Capella. This is consistent with th e association of the broad wings with microflaring since HR 1099 is a very active binary system. In contrast, the transition-region lines of Procyon, a relatively inactive star, do not show evidence for broad w ings, with the possible exception of N v lambda 1239. However, Procyon 's lines do appear to have excess emission in their blue wings. Linsky et al. found no evidence for broad wings in Capella's chromospheric l ines, but we find that the Mg II resonance lines of HR 1099 do have br oad wings. The striking resemblance between HR 1099's Mg II and C IV l ines suggests that the Mg II line profiles may be regulated by turbule nt processes similar to those that control the transition-region line profiles. If this is the case, microflaring may be occurring in the K1 star's chromosphere as well as in its transition region. However, rad iative transfer calculations suggest that the broad wings of the Mg II lines can also result from normal chromospheric opacity effects rathe r than pure turbulence. The prominence of broad wings in the transitio n region and perhaps even chromospheric lines of active stars suggests that microflaring is very prevalent in the outer atmospheres of activ e stars.