Spectroscopic study of pulsations in the atmosphere of roAp star 10 Aql

We present the analysis of spectroscopic time-series observations of the roAp star 10 Aql. Observations were carried out in July 2006 with the UVES and SARG spectrographs and simultaneously with the MOST mini-satellite photometry. All these data were analysed for radial velocity (RV) variations. About 150 lines out of the 1000 measured reveal a clear pulsation signal. Frequency analysis of the spectroscopic data gives three frequencies that coincide with the photometric ones. Phase-amplitude diagrams created for the lines of different elements/ ions show that atmospheric pulsations may be represented by a superposition of standing and running wave components, similar to other roAp stars. The highest RV amplitudes, 300-400 ms-1, were measured for Ce II, Dy III, Tb III, and two unidentified lines at λ 5471, 5556 Å. We discovered a ≈0.4 period phase jump in the RV measurements across the Nd III line profiles, indicating the presence of the pulsation node in stellar atmospheres. The phase jump occurs at nearly the same atmospheric layer for the two main frequencies. There is no rotational modulation in the average spectra for the 6 different nights we analysed.