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   PR # 12019
    Geminga is a rotation-powered,radio-quiet pulsar with period$P=0.237$
    ~s and spin-down age $3.4 \times 10^5$ yr.Geminga affords the most de
    tailed look so far at the surface and environment of a neutron star,&
    how they are affected by the particle accelerator which is reponsible
    for the $\gamma$-rays.Although it is a strong soft X-ray and $\gamma$
    -ray source,Geminga has not yet been studied in the 2--10 keV window.
    The $ASCA$ spectrum & pulse profile will reveal whether the hardX-ray
    component is thermal emission from the hot polar caps,or synchrotron
    emission from the inner magnetosphere.  In conjunction with $ROSAT$,
    $EUVE$, and $EGRET$,the $ASCA$ data will be used to develop a consist
    ent model of the magnetosphere accelerator, surface magnetic field
   geometry,and polar cap heating
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