We combine results from interferometry , asteroseismology and spectroscopy to determine accurate fundamental parameters of 23 bright solar-type stars , from spectral type F5 to K2 and luminosity classes III to V. For some stars we can use direct techniques to determine the mass , radius , luminosity and effective temperature , and we compare with indirect methods that rely on photometric calibrations or spectroscopic analyses .
We use the asteroseismic information available in the literature to infer an indirect mass with an accuracy of 4–15 % .
From indirect methods we determine luminosity and radius to 3 % .
We find evidence that the luminosity from the indirect method is slightly overestimated ( \approx 5 % ) for the coolest stars , indicating that their bolometric corrections are too negative .
For T _ { eff } we find a slight offset of -40 \pm 20 K between the spectroscopic method and the direct method , meaning the spectroscopic temperatures are too high .
From the spectroscopic analysis we determine the detailed chemical composition for 13 elements , including Li , C and O .
The metallicity ranges from { [ Fe / H ] } = -1.7 to +0.4 , and there is clear evidence for \alpha -element enhancement in the metal-poor stars .
We find no significant offset between the spectroscopic surface gravity and the value from combining asteroseismology with radius estimates .
From the spectroscopy we also determine v \sin i and we present a new calibration of macro- and microturbulence .
From the comparison between the results from the direct and spectroscopic methods we claim that we can determine T _ { eff } , \log g , and [ Fe/H ] with absolute accuracies of 80 K , 0.08 dex , and 0.07 dex .
Photometric calibrations of Strömgren indices provide accurate results for T _ { eff } and [ Fe/H ] but will be more uncertain for distant stars when interstellar reddening becomes important .
The indirect methods are important to obtain reliable estimates of the fundamental parameters of relatively faint stars when interferometry can not be used .
Our study is the first to compare direct and indirect methods for a large sample of stars , and we conclude that indirect methods are valid , although slight corrections may be needed .