X-ray pulsars observed with hakucho and tenma

The pulse periods of eight pulsars Her X-1, Cen X-3, Vela X-1, A0535+26, GX301-2, 4U1626-67, 4U1538-52, and OA01657-415, have been measured with HAKUCHO and TENMA satellites between March 1979 and July 1983. Not only the wind-fed X-ray pulsas such as Vela X-1, GX301-2 and A0535-26, but also Her X-1 and Cen X-3, which are considered to be disk-fed pulsars, exhibit a remarkable change in the spin-up rate.