The pulsation of Geminga has been detected to date only at high energies (E>0.1keV). Since X-ray exposures are short and Geminga is at best only marginally detected in γ-rays at E<30MeV, the primary means of timing Geminga is with high-energy γ-rays. The EGRET observations of Geminga now span 4-years. These data are analyzed to determine the 1995 ephemeris for Geminga which is provided here. We continue to count every revolution of Geminga during the GRO mission with a rotational phase resolution which improves with additional exposure. Proper motion is now apparent in γ-ray timing, consistent with the optical measurement of Bignami et al. (1993Natur.361..704B). With improved statistics, two additional peaks are tentatively detected in the ``minor bridge'' region. More exposure is required to confirm them. If found to be real, they are difficult to understand with polar cap models, but are expected for the outer gap model, and provide sorely needed constraints.
Astronomy and Astrophysics Supplement Series
- Pub Date:
- November 1996
- PULSARS: INDIVIDUAL: GEMINGA = 1E 0630+1;