POSSIBLE PULSED OPTICAL-EMISSION FROM GEMINGA

We present optical data which suggests that G '', the optical counterp art of the gamma-ray pulsar Geminga, possibly pulses in B with a perio d of 0.237 seconds. The similarity between the optical pulse shape and the gamma-ray light curve indicates that a large fraction of the opti cal emission is non-thermal in origin - contrary to recent suggestions based upon the total optical flux. The derived magnitude of the pulse d emission is m(B) = 26.0 +/- 0.4. Whilst it is not possible to give a n accurate figure for the pulsed fraction (due to variations in the sk y background) we can give an 1 sigma upper limit of m(B) approximate t o 27 for the unpulsed fraction.