Table 4: Angular diameter determinations with plane-parallel and spherical MARCS models. Only a very small improvement on the chi-square value can be achieved by increasing the extension of the atmosphere of the model (SPH model with $\log{g} = 1.0$ ), and such a low surface gravity cannot be reconciled with the spectral features.
Model PP, 4250 K SPH, 4250 K SPH, 4250 K

$\log g=1.5$ $\log{g} = 1.0$ $\log g=1.5$

$\phi$ (mas) $21.32\pm0.19$ $22.37 \pm 0.19$ $21.84 \pm 0.21$

$\phi_{\tau_{\rm Ross}=1}$ NA $21.16 \pm 0.18$ $21.19 \pm 0.20$

d (Eq. (1)^*) 0.030 0.057 0.030

$\chi ^{2}_{{\rm r}}$ 5.63 5.38 5.51

^* Out to $\tau_{{\rm Ross}} = 10^{-7}$ .

**Table 4:** Angular diameter determinations with plane-parallel and spherical MARCS models. Only a very small improvement on the chi-square value can be achieved by increasing the extension of the atmosphere of the model (SPH model with $\log{g} = 1.0$ ), and such a low surface gravity cannot be reconciled with the spectral features.
Model	PP, 4250 K	SPH, 4250 K	SPH, 4250 K
	$\log g=1.5$	$\log{g} = 1.0$	$\log g=1.5$
$\phi$ (mas)	$21.32\pm0.19$	$22.37 \pm 0.19$	$21.84 \pm 0.21$
$\phi_{\tau_{\rm Ross}=1}$	NA	$21.16 \pm 0.18$	$21.19 \pm 0.20$
d (Eq. (1)^*)	0.030	0.057	0.030
$\chi ^{2}_{{\rm r}}$	5.63	5.38	5.51
^* Out to $\tau_{{\rm Ross}} = 10^{-7}$ .

Source LaTeX | All tables | In the text

	1 Introduction
	2 The interferometric calibration process: The need for well-known calibrators
	3 The observations
	4 Interpretation of the data: Comparison with theoretical atmosphere models
	5 The binary hypothesis
	6 Conclusions and outlook
	References