AAS 207th Meeting, 8-12 January 2006
Session 72 Neutron Stars and X-ray Binaries
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[72.06] X-Ray Eclipse Timing in the LMXB EXO0748-676

M.T. Wolff, P.S. Ray, K.S. Wood (Naval Research Laboratory)

Orbital period changes are an important diagnostic for understanding low mass X-ray binary (LMXB) accretion-induced angular momentum exchange and overall binary system evolution. EXO0748-676 is unique among LMXB systems in that it shows full 492-second eclipses during its 3.82-hour orbital period. Furthermore, unlike other known eclipsing LMXBs (e.g., X1658-298), EXO0748-676 has been X-ray active since its discovery in 1985 allowing us to observe its orbital dynamics in great detail, especially during the RXTE era. We report on our most recent results for the eclipse timing of the LMXB EXO0748-676. Since its discovery in 1985 it has apparently undergone three distinct orbital period “epochs", each characterized by a different orbital period than the previous epoch. We outline the system orbital period behavior for EXO0748-676 over the past 20 years and discuss the implications of this behavior in light of current theoretical ideas for LMXB evolution.

This research was funded by the NASA RXTE Guest Observer Program and the Office of Naval Research.

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