AAS 201st Meeting, January, 2003
Session 12. Activity in Cool Stars
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[12.09] HST/STIS High Resolution Echelle Spectra of \alpha Centauri A (G2 V)

J.L. Linsky (JILA/Univ. Colorado), I. Pagano (Catania Astro. Obs.), J. Valenti (Space Telescope Sci. Inst.), M. Gagne (West Chester Univ.), D.K. Duncan (Univ. Colorado)

We report on HST/STIS observations of the G2 V star \alpha~Centauri~A (HD 128620), a near twin to the Sun. The high resolution echelle spectra obtained with the E140H and E230H gratings cover the complete spectral range 1133--3150~Å\ with a resolution of 2.6 km~s-1. This beautiful spectrum contains a very large number of emission and absorption lines. We present our study of the E140H spectrum. Of particular interest are the shapes of the transition region lines (e.g., Si~IV, C~IV), the density sensitive intersystem lines, and the He~II 1640~Å\ line. Our purpose is to compare the \alpha~Cen~A UV spectrum with the solar spectrum to determine how the atmosphere and heating processes in \alpha~Cen~A differ from the Sun as a result of the small differences in gravity, age, and chemical composition of the two stars.

The \alpha~Cen~A spectral atlas can serve as a useful spectral atlas for the Sun as a star because the STIS spectrum is a true full disk average with limb darkening, covers a broad spectral range, has very high spectral resolution, and has excellent wavelength precision and absolute flux calibration.

This work is supported by grant GO-07263 from the Space Telescope Science Institute, which is operated by AURA, Inc. under NASA contract NAS 5-26555.

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