HST/STIS high resolution echelle spectra of α Centauri A (G2 V) *,**
INAF, Catania Astrophysical Observatory, via Santa Sofia 78, 95125 Catania, Italy e-mail: firstname.lastname@example.org
2 JILA, University of Colorado and NIST, Boulder, CO 80309-0440, USA e-mail: email@example.com
3 Space Telescope Science Institute, 3700 San Martin Dr. Baltimore, MD 21218, USA e-mail: firstname.lastname@example.org
4 Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0389, USA e-mail: email@example.com
Corresponding author: I. Pagano, firstname.lastname@example.org
Accepted: 9 October 2003
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 1133-3150 Å with a resolution of 2.6 km s-1, an absolute flux calibration accurate to %, and an absolute wavelength accuracy of 0.6–1.3 km s-1. We present here a study of the E140H spectrum covering the 1140–1670 Å 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., , ), infer the electron density from the 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.
Key words: stars: individual: α Cen A / stars: chromospheres
Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposal GO-07263.
© ESO, 2004