2008A&A...490.1109M

We investigate the oscillation spectrum of the most chemically-peculiar star in the sky, the rapidly-oscillating magnetic (roAp) star HD 101065. High-precision radial velocity (RV) measurements, spanning four consecutive nights on 3-6 March, 2004, were obtained with the HARPS echelle-spectrometer at the ESO 3.6-m telescope, and photometric data were acquired during 6 nights of observations at the 24-inch telescope of Siding Spring Observatory. The RVs were measured using all spectral lines in the wavelength range 4400-5100Å. We detected a rich spectrum of oscillation modes with semi-amplitudes ranging between 217m/s and 1.6m/s. These belong to the complete spectrum of high-order, low l=0-2 modes, having a large spacing of <Δν≥64.07±0.9µHz. We calculated the nonadiabatic frequencies of axisymmetric high-order p-modes for main-sequence models with dipole magnetic fields of two chemical compositions (X,Z)=(0.7,0.02) and (X,Z)=(0.695,0.025). The former composition provided the best fit model and yielded stellar parameters of mass, M=1.525±0.025M_☉, age=(1.5±0.1)x10⁹yr, effective temperature log T_e=3.821±0.006, luminosity logL/L_☉=0.797±0.026, surface gravity logg=4.06±0.04, and polar magnetic field strength, Bp=8.7±0.3kG. We are able to identify the modes of all detected oscillation frequencies. The photometric U and B light curves have maxima that precede the RV maximum by 0.16-0.19 in phase.