H-alpha spectroscopy of the recurrent nova RS Oph during the 2021 outburst

We report spectroscopic observations of the $H\alpha$ emission line of the recurrent nova RS~Oph obtained between 12 and 23 August 2021 during the recent outburst. On the basis of the sharp P~Cyg profile superimposed onto the strong H-alpha emission, we estimate that the outflowing velocity of the material surrounding RS Oph is in the range 32 km/s < V_{out} < 68 km/s. The new GAIA distance indicates that the red giant should be probably classified in between II and III luminosity class. The spectra are available upon request from the authors and on Zenodo.