We phase fold the spectra onto the known dominant period of 2.80746mHz, to study the abundances and line-broadening as a function of pulsation phase. The abundances do not stand out against those of other subdwarf B stars, hence we find no evidence to suggest that the richness of the frequency spectrum and/or the high pulsation amplitudes are related to abundance effects. The abundances do not change with pulsational phase.

The metal lines in Balloon 090100001 are much broader than for non-pulsating subdwarfs, and during the cycle of the main pulsation the line broadening varies with ∼ 2 km/s amplitude. Hence we find clear evidence for pulsational broadening of the lines.

We combined the information content of 56 narrow absorption lines through a cross-correlation technique, to create cross-correlation functions that for each individual pulsation phase approximate the average line-profile shape. The resulting profiles have sufficient signal-to-noise for a mode-identification analysis.

To fit the line profiles we consider all modes with ℓ ≤ 2 and associated |m|, and use a model of the 3D pulsational surface velocity field. The models with ℓ = 2 do not fit the profiles. The best fit is obtained from the model of a radial pulsation (ℓ = 0).