HEAD 2000, November 2000
Session 24. X-Ray Binaries - Timing and Transients
Display, Wednesday, November 8, 2000, 8:00am-6:00pm, Bora Bora Ballroom

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[24.09] Long term hard X-ray periodic modulations of 8 HMXBs

M. J. Coe, S.G.T. Laycock (Southampton University), B.A. Harmon, M. Finger, C.A. Wilson (NASA/MSFC)

In this paper we will present results obtained from the BATSE occultation data base covering over 7 years of continuous observation in the 20-70 keV band. The eight objects studies are all High Mass X-ray Binaries (HMXB) with known binary or disk precession periods.

We have searched the data base for evidence of hard X-ray modulation at the previously known periods and will present lightcurves for eight objects. In addition we have done Monte Carlo simulations to assess the significance of detected features in these lightcurves.

The main conclusions from this work are:

- Binary or precession lightcurves for 8 objects

- A more accurate value for the disk precession period in LMC X-4

- Strong evidence for apastron outbursts in three systems

- Remarkably little evidence for variability in switch-on times for the Type 1 X-ray outbursts in these systems

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