AAS 203rd Meeting, January 2004
Session 48 Fully Employed Stars
Poster, Tuesday, January 6, 2004, 9:20am-6:30pm, Grand Hall

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[48.03] The UV Spectrum of the Flare Star EV Lacertae

C. Roark (The University of Iowa), R. Osten (National Radio Astronomy Observatory)

This study is part of a multi-wavelength survey using UV time-tagged data from four orbits of the HST to study the flare star EV Lacertae. By extracting the data in 60s intervals we were able to create light curves, determine the quiescent and flaring times and make respective spectra ranging from 1140 to 1735 Å. These spectra contain ionic transitions with formation temperatures between about 1e4 and 1e5 K, which probe the chromosphere and transition region in the outer atmosphere of EV Lac. While fitting both the quiescent and flare spectral emission lines with Gaussian curves, broad wings were discovered in the high formation temperature lines of the quiescent stages, thus requiring multiple Gaussians. The peak flare count rates were enhanced approximately 2-3 times the quiescent count rate and lasted a few minutes at most. The average continuum was determined to be 1.2e-15 erg cm-2 s-1 Å-1 for the quiescent times and 2.6e-15 erg cm-2 s-1 Å-1 for the flaring, which are both relatively small compared to the line fluxes and didn't need to be taken into account during line fitting. Using Chianti we were able constrain a viable range (2.3e11 to 3.8e11) to the electron density of OV by calculating the line ratio of 1218 to 1371 Å.

This research is part of the NSF REU program and also received funding from STScI through grant #GO-08880.09-A.

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Bulletin of the American Astronomical Society, 35#5
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