Recent timing studies on RXTE observations of 4U 1538-52
A. BaykalPhysics Department, Middle East Technical University, 06531 Ankara, Turkey e-mail: [email protected]S. Ç. İnamDepartment of Electrical and Electronics Engineering, Başkent University, 06530 Ankara, Turkey e-mail: [email protected]E. BeklenPhysics Department, Middle East Technical University, 06531 Ankara, Turkey e-mail: [email protected]
2006en
ABI
Abstract
The high mass X-ray binary pulsar 4U 1538-52 was observed between July 31 and August 7, 2003. Using these observations, we determined new orbital epochs for both circular and elliptical orbit models. The orbital epochs for both orbit solutions agreed with each other and yielded an orbital period derivative yr-1. This value is consistent with the earlier measurement of yr-1 at the level and gives only an upper limit to the orbital period decay. Our determination of the pulse frequency showed that the source spun up at an average rate of Hz s-1 between 1991 and 2003.
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