Essentially all classes of stars possessing a soft X-ray emitting
corona also have members which show transient energetic activity. The
activity manifests itself in powerful flares, with individual events
releasing 
times the energy of a strong solar flare. These
include the classical flare stars (the UV Cet or dMe stars), the RS
CVn binaries, and the pre-main sequence weak-line T Tauri (WTT) stars.
The flares are accompanied by radio bursts. At frequencies 
GHz the dMe stars emit bursts of highly circularly polarized coherent
radiation with a brightness temperature exceeding 
K at
times. The emission shows a rich variety of structure in both the time
and frequency domains. The emission mechanisms have not yet been
identified. The RS CVn stars also display broadband, highly circularly
polarized, and extremely bright radio bursts at times. Observations
to date have been hampered by insufficient spectral coverage and
insufficient temporal resolution (which requires high sensitivity).
An exciting possibility is to exploit the broadband spectral
processing capabilities of the new correlator to perform spectroscopic
observations of coherent bursts on stars. The motivations for doing so
are several: i) to date, spectral observations of stellar radio bursts
have only been possible over relative bandwidths 
few percent. The possibility of processing 500 MHz of IF bandwidth
instantaneously will allow access to relative bandwidths of several
tens of percent, sufficient to resolve structures drifting in the
frequency domain (electron beams and MHD shocks); ii) elucidation of
the spectral properties of these bursts, of which there are no analogs
on the Sun, may allow identification of the relevant emission
mechanisms; iii) the extremely high brightness temperatures of
these bursts may drive phenomena which are inaccessible to study in
other astrophysical objects: e.g., stimulated Compton or Raman
scattering.
It should also be pointed out that the incoherent synchrotron and gyrosynchrotron emission from the dMe stars offers a direct diagnostic of physical parameters in the flaring source. Because it is relatively weak (few to a few tens of mJy) the study of incoherent flare emissions would benefit enormously from the high frequency receiver upgrades.
The study of all active stars would benefit from the enhanced frequency coverage and agility proposed in the VLA Development Plan, allowing observers to obtain broad-band spectra of the evolving source over relatively short timescales.