Long-term X-ray observations of CEN X-3, GX 301-2 (4U 1223-62), GX 304-1 (4U 1258-61) and 4U 1145-61.

Ten-day time resolution X-ray time histories are presented from the 1969-1976 period, for the sources Cen X-3, GX 301-2, GX 304-1, and 4U 1145-61. Three of the four sources examined show periods in excess of one month, in keeping with the model in which these sources are neutron stars in eccentric orbits around early type stars, accreting matter from the stellar wind. Vela data confirm the suggested period of 41.5 days for GX 301-2, and strengthen the case for a 187.5-day 4U 1145-61 period. GX 304-1 has a 132.5-day period manifested by sharply peaked outbursts.