AAS Meeting #193 - Austin, Texas, January 1999
Session 99. Stellar Atmospheric Activity and Luminous Blue Variables
Display, Saturday, January 9, 1999, 9:20am-4:00pm, Exhibit Hall 1

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[99.06] FUV Observations of Flares on the dM0e star AU Mic

R.D. Robinson (IACS/CUA), J.L. Linsky (JILA), B. Woodgate (GSFC/NASA), L. Carkner (JILA), G. Timothy (Nightsen Inc.)

We report on FUV observations of stellar flares on the dM0e star AU Microscopii obtained on 1998 Sept 06 with the Space Telescope Imaging Spectrograph (STIS) aboard the {\em Hubble Space Telescope}. The data consist of medium resolution echelle observations covering the wavelength region from 1170-1730 Å\ with a resolution of 45,800. The observations were obtained using the TIME-TAG observing mode in which the time and position of each detected photon is recorded. This allows an analysis of variability which is limited only by the counting statistics of the data.

During a total on-source time of 10,000 s we observed numerous microflare bursts as well as 4 well defined flare events. These flares lasted between 1 and 3 minutes and and were most easily observed in the FUV continuum and the Si~IV and C~IV resonance lines. Variations in both the cooler (e.g. Ly\alpha, C~II, O~I) and hotter (O~V, N~V, Fe~XXI) emission lines were much less pronounced.

In this paper we will examine the physical characteristics of the main flare events. This discussion will include the time history of the wavelength integrated fluxes in the continuum and various emission lines. In particular, we search for increased emission in the red wing of the Ly\alpha line which would indicate the presence of moderately energetic proton beams. We also integrate the time sequences over the entire flare duration and investigate the average line and continuum properties during each of the events, including flows and turbulence as a function of temperature as well as the shape of the FUV continuum. Unfortunately, none of the events was strong enough to allow a detailed examination of line profiles as a function of time.

This work is supported by NASA grants to the Catholic University of America and the University of Colorado.

The author(s) of this abstract have provided an email address for comments about the abstract: robinson@opal.gsfc.nasa.gov

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