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

Free access article

Issue		A&A Volume 400, Number 2, March III 2003


Page(s)		695 - 707
Section		Formation and evolution of planetary systems
DOI		http://dx.doi.org/10.1051/0004-6361:20021790

A&A 400, 695-707 (2003)
DOI: 10.1051/0004-6361:20021790

III. A0 to G2 stars

L. Decin¹, B. Vandenbussche¹, C. Waelkens K. Eriksson^{1, 2}, 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)

Abstract
Vega, Sirius, $\beta$ Leo, $\alpha$ Car and $\alpha$ Cen A belong to a sample of twenty stellar sources used for the calibration of the detectors of the Short-Wavelength Spectrometer on board the Infrared Space Observatory (ISO-SWS). While general problems with the calibration and with the theoretical modelling of these stars are reported in Decin et al. (2003), each of these stars is discussed individually in this paper. As demonstrated in Decin et al. (2003), it is not possible to deduce the effective temperature, the gravity and the chemical composition from the ISO-SWS spectra of these stars. But since ISO-SWS is absolutely calibrated, the angular diameter ( $\theta_{\rm d}$ ) of these stellar sources can be deduced from their ISO-SWS spectra, which consequently yields the stellar radius ( R), the gravity-inferred mass ( $M_{\rm g}$ ) and the luminosity ( L) for these stars. For Vega, we obtained $\mbox{$\theta_{\rm d}$ }= 3.35 \pm 0.20$ mas, $R = 2.79 \pm 0.17$ $R_{\odot}$ , $M_{\rm g} = 2.54 \pm 1.21$ $M_{\odot}$ and $L = 61 \pm 9$ $L_{\odot}$ ; for Sirius $\mbox{$\theta_{\rm d}$ }= 6.17 \pm 0.38$ mas, $R = 1.75 \pm 0.11$ $R_{\odot}$ , $M_{\rm g} = 2.22 \pm 1.06$ $M_{\odot}$ and $L = 29 \pm 6$ $L_{\odot}$ ; for $\beta$ Leo $\mbox{$\theta_{\rm d}$ }= 1.47 \pm 0.09$ mas, $R = 1.75 \pm 0.11$ $R_{\odot}$ , $M_{\rm g} = 1.78 \pm 0.46$ $M_{\odot}$ and $L = 15 \pm 2$ $L_{\odot}$ ; for $\alpha$ Car $\mbox{$\theta_{\rm d}$ }= 7.22 \pm 0.42$ mas, $R = 74.39 \pm 5.76$ $R_{\odot}$ , $M_{\rm g} = 12.80^{+24.95}_{-6.35}$ $M_{\odot}$ and $L = 14573 \pm 2268$ $L_{\odot}$ and for $\alpha$ Cen A $\mbox{$\theta_{\rm d}$ }= 8.80 \pm 0.51$ mas, $R = 1.27 \pm 0.08$ $R_{\odot}$ , $M_{\rm g} = 1.35 \pm 0.22$ $M_{\odot}$ and $L = 1.7 \pm 0.2$ $L_{\odot}$ . These deduced parameters are confronted with other published values and the goodness-of-fit between observed ISO-SWS data and the corresponding synthetic spectrum is discussed.

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

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

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