2006MNRAS.371.1497W

We report the serendipitous discovery of the Sloan Digital Sky Survey (SDSS) star SDSS J160043.6+074802.9 to be a very rapid pulsator. The variation is dominated by a frequency near 8380µHz (period = 119.33s) with a large amplitude (0.04mag) and its first harmonic at 16760µHz (59.66s; 0.005mag). In between these frequencies, we find at least another eight variations with periods between 62 and 118s and amplitudes between about 0.007 and 0.003mag; weaker oscillations might also be present. Preliminary spectrograms from the performance verification phase of the Southern African Large Telescope indicate that SDSS J160043.6+074802.9 is a spectroscopic binary consisting of an sdO star and a late-type main-sequence companion. This makes it the first unambiguous detection of such an sdO star to pulsate, and certainly the first found to exhibit multifrequency variations.