X-RAY PULSATIONS IN THE SUPERSOFT X-RAY BINARY CAL 83

Chandra and XMM-Newton X-ray data reveal that the supersoft X-ray binary CAL 83 exhibits 38.4 minute pulsations at some epochs. These X-ray variations are similar to those found in some novae and are likely to be caused by nonradial pulsations of the white dwarf. This is the first detection of pulsations in a classical supersoft X-ray binary.