Pulse-Period Changes of X-Ray Pulsars Measured with Hakucho and Tenma

Abstract Eight X-ray pulsars, Her X-1, Cen X-3, 4U 1626–67, OAO 1657–415, A 0535+26, Vela X-1, 4U 1538–52, and GX 301–2, have been observed from Hakucho and Tenma. The pulse periods of all these X-ray pulsars measured with Hakucho and Tenma between March 1979 and October 1983 are summarized together with those of 4U 1700–37 and 4U 1907+09, the pulsations of which were newly discovered by Tenma observations. Several instances of remarkable behavior in pulse-period change are revealed both for the wind-fed and disk-fed pulsars.