HEAD Division Meeting 1999, April 1999
Session 15. X-Ray Binaries
Poster, Tuesday, April 13, 1999, 8:30am-6:02pm, Gold Room

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[15.18] A Survey of the 30.5 Day Cycle in LMC X-4

Matthew Scott (USRA/MSFC), Denis Leahy (Univ. of Calgary)

LMC X-4 is a high mass X-ray binary system with a 13.5 sec period accreting pulsar in a 1.4 day orbit. The system displays a super-orbital cycle of X-ray intensity variations repeating every 30.5 days consisting of alternating high and low X-ray flux state. This phenomenon is believed to be caused by a tilted, precessing accretion disk similar to that in Her X-1. We present results of a study of the 30.5 day ``long'' cycle of LMC X-4 using RXTE observations. The 30.5 day cycle was surveyed with a series of RXTE pointings. We present the resulting lightcurve and compare it to the average lightcurve obtained from the RXTE All-Sky Monitor. We show color-color and color-intensity plots as well as representative spectra. The pulse profile evolution across the single High state of LMC X-4 is shown. There is no evidence for a second weaker high state in LMC X-4 unlike that in Her X-1. We compare the properties of the long cycle in LMC X-4 with those in Her X-1.

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