Communications in Asteroseismology 162, pp. 3-20, 2011/11/30
Crawford’s uvby ß calibration method is examined for A-type stars by comparing it with the pulsational variations of the observable m1, c1 and MV for the δ Scuti star FG Vir. The fit between the calibration values of m1 and MV and the respective measurements for FG Vir are tested as a function of temperature based on 3068 4-colour values taken at the Observatorio de Sierra Nevada in Spain during the years 2002 and 2003. Testing is performed by means of linear regression. The fit between the measured index m1 of FG Vir and the m1 index of the Hyades is nearly perfect. A fit between the calibration value MV and the measured values of FG Vir cannot be obtained with Crawford’s calibration procedure in a straightforward manner. In order to achieve an optimal fit for MV two modifications of the calibration procedure are investigated and discussed. (i) the position of the ZAMS given by Crawford is replaced by the position of the ZAMS given by Mermilliod; (ii) the influence of the mass difference on c1 is taken into account.
