EDP Sciences
Free access
Volume 400, Number 2, March III 2003
Page(s) 709 - 727
Section Formation and evolution of planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20021786

A&A 400, 709-727 (2003)
DOI: 10.1051/0004-6361:20021786

ISO-SWS calibration and the accurate modelling of cool-star atmospheres

IV. G9 to M2 stars
L. Decin1, B. Vandenbussche1, C. Waelkens1, G. Decin1, K. Eriksson2, B. Gustafsson2, B. Plez3 and A. J. Sauval4

1  Instituut voor Sterrenkunde, KULeuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
2  Institute for Astronomy and Space Physics, Box 515, 75120 Uppsala, Sweden
3  GRAAL - CC72, Université de Montpellier II, 34095 Montpellier Cedex 5, France
4  Observatoire Royal de Belgique, Avenue Circulaire 3, 1180 Bruxelles, Belgium

(Received 22 November 2001 / Accepted 2 December 2002 )

A detailed spectroscopic study of 11 giants with spectral type from G9 to M2 is presented. The 2.38-4.08  $\mu$m wavelength-range of band 1 of ISO-SWS (Short-Wavelength Spectrometers on board of the Infrared Space Observatory) in which many different molecules - with their own dependence on each of the stellar parameters - are absorbing, enables us to estimate the effective temperature, the gravity, the microturbulence, the metallicity, the CNO-abundances, the 12C/13C-ratio and the angular diameter from the ISO-SWS data. Using the Hipparcos' parallax, the radius, luminosity and gravity-inferred mass are derived. The stellar parameters obtained are in good agreement with other published values, though also some discrepancies with values deduced by other authors are noted. For a few stars ( $\delta$ Dra, $\xi$ Dra, $\alpha$ Tuc, H Sco and $\alpha$ Cet) some parameters - e.g. the CNO-abundances - are derived for the first time. By examining the correspondence between different ISO-SWS observations of the same object and between the ISO-SWS data and the corresponding synthetic spectrum, it is shown that the relative accuracy of ISO-SWS in band 1 (2.38-4.08  $\mu$m) is better than 2% for these high-flux sources. The high level of correspondence between observations and theoretical predictions, together with a confrontation of the estimated Teff (ISO) value with Teff values derived from colours - which demonstrates the consistency between V-K, BCK, Teff and $\theta_{\rm d}$ derived from optical or IR data - proves that both the used MARCS models to derive the stellar quantities and the flux calibration of the ISO-SWS detectors have reached a high level of reliability.

Key words: infrared: stars -- stars: atmospheres -- stars: late-type -- stars: fundamental parameters

Offprint request: L. Decin, Leen.Decin@ster.kuleuven.ac.be

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