脉冲星Geminga MeV 脉冲辐射证据

利用直接解调方法分析COMPTELVPI数据，得到了脉冲星Geminga10-30MeV脉冲辐射存在的证据：全位相及分位相成像均得到了Geminga．分位相成像结果显示，光变曲线的峰值位于pulse1附近，而其它位相区域只能给出上限．由于成像分析不存在选择效应，该成像结果表明，Geminga在MeV能区仍存在脉冲辐射．虽然Geminga的弱MeV辐射使得很难就VP1数据作时间分析，但仍得到了一些周期信号的迹象，并且与成像结果不相矛盾．进一步考察EGRET观测Geminga在30MeV以上的强度比Pulse2／Pulse1，发现在VP1观测的较低能区，Pulse1有渐强于Pulse2的趋势，这和我们在MeV能区的成像及时间分析结果相一致．成像得到的流强表明，Geminga的能谱至少在10MeV以上不应出现偏折．

Evidence for Pulsed MeV Emission from Pulsar Geminga

Evidence for 10-30 MeV pulsation from Geminga has been obtained in our reanalysis of the data from COMPTEL individual observation VP 1 with a direct demodulation method. Images of Geminga from both full phase data and phase-resolved data were derived in the energy range fly30 MeV for VP 1. Imaging results from the phase-resolved data show that maximum of the light curve is in the phase region of pulse 1 and only upper limits can be given for the other three phase regions. Our imaging analyses are free from any selection effects and, therefore, give evidence for MeV pulsation from Geminga during VP 1. The 10-30 MeV timing analysis of Geminga for VP 1 is difficult due to the weakness of Geminga and the obtained faint indication, however, seems consistent with the imaging results obtained from phase-resolved data. Further check of intensity ratio of pulse 2/pulse 1 measured by EGRET at energies above 30 MeV during VP1 suggests that intensity of pulse 1 should be stronger than that of pulse 2 at MeV energies, which is consistent with our COMPTEL results. With the obtained 10-30 MeV flux, we find the spectrum of Geminga does not show any break, at least at energies above 10 MeV.