AAS 205th Meeting, 9-13 January 2005
Session 102 Neutron Stars
Poster, Wednesday, January 12, 2005, 9:20am-6:30pm, Exhibit Hall

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[102.10] Phase Variation in the Pulse Profile of SMC X-1

J.M. Neilsen (Kenyon College), R.C. Hickox, S.D. Vrtilek (CfA)

We present the results of timing and spectral analysis of X-ray high state observations of the massive X-ray binary system SMC X-1 from \textit{Chandra}, \textit{XMM-Newton}, and \textit{ROSAT}, taken between 1991 October and 2001 November. The source showed L\rm X~ 3-5\times1038 ergs s-1, and the spectrum was modelled as a power law plus a blackbody with kT\rm bb~0.18 and reprocessed emission radius R\rm bb~2\times 108 cm. We have assumed a distance of 60 kpc to the source. Pulse profiles extracted from the observations show a number of distinct forms, more than half of which include a second pulse in the soft profile, previously documented only in hard energies. We also detect strong variation in the phase shift between hard and soft pulse profiles, as has recently been reported in Her X-1. We suggest an explanation for the observed characteristics of the soft pulses with considerations of the precession of the accretion disk. This research was made possible by NSF grants 9731923 and AST 0307433 and NASA grant NAG5-10780.

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