The determination of the rotation period and magnetic field geometry of the strongly magnetic roAp star HD 154708

We obtained 13 spectropolarimetric observations of the strongly magnetic rapidly oscillating Ap star HD 154708 over 3 months with the multimode instrument FORS 1, installed at the 8-m Kueyen telescope of the Very Large Telescope. These observations have been used for the determination of the rotation period of P = 5.3666 +/- 0.0007 d. Using stellar fundamental parameters and the longitudinal magnetic field phase curve, we briefly discuss the magnetic field geometry. The star is observed nearly pole-on and the magnetic field geometry can be described by a centred dipole with a surface polar magnetic field strength B-d between 26.1 and 28.8 kG and an inclination of the magnetic axis to the rotation axis in the range 22 degrees.5 to 35 degrees.5.