Alpha Centauri: coronal temperature structure and abundances from ASCA observations

Details Alpha Centauri: coronal temperature structure and abundances from ASCA observations Alpha Centauri: coronal temperature structure and abundances from ASCA observations

Nov 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998a%26a...339..545m&link_type=abstract

Astronomy and Astrophysics, v.339, p.545-552 (1998)

Astronomy and Astrophysics

Astrophysics

5

Stars: Coronae, Stars: Individual: Alpha Cen, Stars: Abundances, X-Rays: Stars

Scientific paper

We have analyzed the X-ray spectrum of the nearby binary alpha Cen AB (G2V + K1V) that has been obtained from observations with ASCA. The coronal temperature structure and abundances have been derived from multi-temperature fitting and confirmed by a differential emission measure analysis. The corona as seen by ASCA is essentially isothermal with a temperature around 0.3 keV, consistent with the evolutionary picture of coronae of aging solar-type stars. A comparison between the measurements from various instruments indicates a source variability in the coronal flux (which precludes the joint fitting of data from different instruments taken at different epochs) and temperature structure consistent with that discovered in a series of ROSAT observations. The elemental abundances agree with solar photospheric abundances for Ne, Si, and Fe at 1hbox {\sigma^2 CrB}ma level, while O appears to be underabundant by a factor of about 3 relative to solar photospheric values, and Mg overabundant by a factor of a few. The abundance ratios with respect to Fe are better determined: [O/Fe] = 0.4+/-0.14 (x solar, etc.), [Mg/Fe] = 4+/-1, [Ne/Fe] = 1+/-0.3, and [Si/Fe] = 6+/-4.

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