Hertzsprung-Russell diagram, zoomed in on the region covered by the five object in the direction of the Galactic disk. The labelled points with the red vertical error bars indicate the standard case (Fig. 2). They are connected by green lines to the points with the green vertical error bars indicating the cases where the effective temperature is fixed to the value determined from spectroscopy, which in turn are connected by blue lines to the points with blue vertical error bars indicating the cases where the effective temperature is fixed to a value roughly in the middle of the IS.