Time-series Spectroscopy of Pulsating sdB stars III: Line Indices of   PG1605+072
  We present the detection and analysis of line index variations in the pulsating sdB star PG 1605+072. We have found a strong dependence of line index amplitude on Balmer line order, with high-order Balmer line amplitudes up to 10 times larger than H-beta. Using a simple model, we have found that the line index may not only be dependent on temperature, as is usually assumed for oscillating stars, but also on surface gravity. This information will provide another set of observables that can be used for mode identification of sdBs. 
S. J. O'Toole, M. A. S. G. Joergensen, H. Kjeldsen, T. R. Bedding, T.   H. Dall and U. Heber