TEV GAMMA-RAY OBSERVATIONS OF COMPTON GAMMA-RAY OBSERVATORY PULSARS -EVIDENCE AGAINST INVERSE-COMPTON CONTROLLED OUTER GAPS

We present the first results of TeV gamma-ray observations of the Comp ton Gamma-Ray Observatory gamma-ray pulsar PSR 1706-44, indicating a s pectral cutoff between approximately 20 GeV and 600 GeV. Improved uppe r limits are also presented for the Vela pulsar and PSR 1509-58. These and other TeV results confirm similar cutoffs for these gamma-ray pul sars as well as for Geminga. The polar cap model predicts such a spect ral cutoff due to magnetic pair production, whereas the outer gap mode l for Vela-type pulsars predicts a similar cutoff resulting from the m aximum synchrotron energy in the outer gap. The spectral flattening be low a certain minimum energy, seen from all of these pulsars, is also consistent with the outer gap prediction. The predicted fluxes of TeV gamma-rays for Vela and Geminga are, however, much larger than the obs erved upper limits. These TeV observations place constraints on any pu lsar model which employs the inverse-Compton scattering of soft photon s by primary TeV electrons at distances relatively far from the stella r surface.