Evidence for an increasing 59 S period in the X-ray emission from Geminga

Abstract

Einstein Observatory and EXOSAT X-ray data from 1E0630 + 178 reveal an approximately 50-percent periodic emission at about 59 s or more. This confirms the early SAS-II and COS-B findings on 2CG 195 + 04 at E greater than 50 MeV and provides the temporal signature for the identification of Geminga. The observations, spanning over a decade (1973-1983), also suggest a very high positive period derivative which has become still higher in 1979-1983.