HEAD 2000, November 2000
Session 42. Stars and Stellar Coronae
Display, Friday, November 10, 2000, 8:00am-6:00pm, Bora Bora Ballroom

## [42.04] High-Resolution X-Ray Spectroscopy of the Late-Type binary system \alpha Centauri with the LETGS on Chandra

R.L.J. van der Meer, A.C. Brinkman, J.S. Kaastra, R. Mewe (Space Research Organization Netherlands), A.J.J. Raassen (SRON & Astronomical Institute, Anton Pannekoek'', Amsterdam, The Netherlands)

We have analyzed high-resolution (\Delta\lambda ~q~0.06~Å) X-ray spectra in the wavelength region from 5 - 175~Å\ of the coronae of the nearby binary \alpha Centauri (G2V + K1V). This binary system, which is separated by 16\prime\prime, was observed with the Chandra LETG/HRC-S spectrometer at 25 December 1999. The dispersion axis was positioned nearly perpendicularly to the axis of the binary, resulting in two separated spectra. It is the first time that the X-ray spectra of the two binary components could be studied separately and simultaneously. The spectra of both components look much alike and have comparable fluxes. This is in contrast with earlier ROSAT observations where a flux ratio of 1:2 was found. The emission measures peak at slightly diffent temperatures around 1-3~MK. He-like ions of O, N, and C, emitting temperature- and density-dependent resonance, forbidden and intercombination lines, have been observed in the lower wavelength region (\lambda~<~45~Å). Si-lines have been observed in the wavelength region around 50~Å\ in a variety of ionization stages (Si~X - Si~XII), while at long wavelengths the spectrum is dominated by the Fe~IX (171.1~Å) and Fe~X (174.5~Å). These lines are known from previous EUVE observations. Using the SPEX90 code, developed at SRON, multi-temperature fits of the entire spectrum, have been made.

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The author(s) of this abstract have provided an email address for comments about the abstract: R.L.J.van.der.Meer@sron.nl

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