Issue |
A&A
Volume 415, Number 1, February III 2004
|
|
---|---|---|
Page(s) | 331 - 348 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20034002 | |
Published online | 03 February 2004 |
HST/STIS high resolution echelle spectra of α Centauri A (G2 V) *,**
1
INAF, Catania Astrophysical Observatory, via Santa Sofia 78, 95125 Catania, Italy e-mail: ipa@ct.astro.it
2
JILA, University of Colorado and NIST, Boulder, CO 80309-0440, USA e-mail: jlinsky@jila.colorado.edu
3
Space Telescope Science Institute, 3700 San Martin Dr. Baltimore, MD 21218, USA e-mail: valenti@stsci.edu
4
Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0389, USA e-mail: dduncan@colorado.edu
Corresponding author: I. Pagano, ipa@ct.astro.it
Received:
25
June
2003
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
© ESO, 2004
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