2004A&A...415..331P

We describe and analyze HST/STIS observations of the G2 V star α Centauri A (α Cen A, HD 128620), a star similar to the Sun. The high resolution echelle spectra obtained with the E140H and E230H gratings cover the complete spectral range 1133-3150Å with a resolution of 2.6km/s, an absolute flux calibration accurate to ±5%, and an absolute wavelength accuracy of 0.6-1.3km/s. We present here a study of the E140H spectrum covering the 1140-1670Å spectral range, which includes 671 emission lines representing 37 different ions and the molecules CO and H₂. For α Cen A and the quiet and active Sun, we intercompare the redshifts, nonthermal line widths, and parameters of two Gaussian representations of transition region lines (e.g., SiIV, CIV), infer the electron density from the OIV intersystem lines, and compare their differential emission measure distributions. One purpose of this study is to compare the α Cen A and solar UV spectra to determine how the atmosphere and heating processes in α Cen A differ from the Sun as a result of the small differences in gravity, age, and chemical composition of the two stars. A second purpose is to provide an excellent high resolution UV spectrum of a solar-like star that can serve as a proxy for the Sun observed as a point source when comparing other stars to the Sun.