Spectroscopy of Pulsating sdB Stars : PG 1605 + 072 1

Received ; accepted – 2 – ABSTRACT We report the detection of velocity variations in the pulsating sdB star, PG 1605+072. Oscillations are detected at the same frequencies found from photom-etry and have amplitudes of up to 14 km s −1 for Hβ. The strongest oscillation found in previous photometric observations is not evident in our spectroscopy or photometry, and may be absent due to beating of closely spaced modes. Phase differences between spectroscopy and B magnitude photometry imply that maximum brightness occurs not long after maximum radius. We have also found evidence of variation in the observed amplitudes of five Balmer lines, with a decrease in amplitude of the strongest mode blueward from Hβ. This effect is not expected and a longer time-series will be needed to clarify it.