The bright southern Cepheid β Doradus: the radial velocity curve, distance and size

A new high-accuracy velocity curve is presented for the bright southern Cepheid β Doradus (HR 1922), and an investigation into the long-term stability of the velocity curve is made. An upper limit of 0.57 km s−1 is placed on cycle-to-cycle variations. This work is compared with a similar analysis previously applied to the long-period Cepheid l Carinae (HR 3884). Using a near-infrared variant of the Barnes-Evans method, the mean radius of and distance to β Dor are found to be R = 67.8 ± 0.7 R⊙ and d = 349 ± 4 pc. The systematic errors in these parameters are less than 3 per cent. If these systematics can be resolved, through the development of advanced theoretical models and/or the direct measurement of angular diameters, a calibration of the cosmic distance scale to better than 1 per cent can be achieved.