Modeling the precession of the warped inner accretion disk in the pulsars LMC X-4 and SMC X-1 with NuSTAR and XMM-Newton

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1909.10559.pdf (3.52 MB)

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https://arxiv.org/abs/1909.10559

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http://hdl.handle.net/11603/16280

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UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
UMBC Faculty Collection

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2019-09-23

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journal articles preprints
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Citation of Original Publication

McKinley C. Brumback and Ryan C. Hickox and Felix S. Fürst and Katja Pottschmidt and John A. Tomsick and Jörn Wilms,Modeling the precession of the warped inner accretion disk in the pulsars LMC X-4 and SMC X-1 with NuSTAR and XMM-Newton, 2019, https://arxiv.org/abs/1909.10559

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Subjects

broad-band X-ray study
superorbital periods
warped inner accretion disk
pulsars
NuSTAR and XMM-Newton

Abstract

We present a broad-band X-ray study of the effect of superorbital periods on X-ray spectra and pulse profiles in the neutron star X-ray binaries LMC X-4 and SMC X-1. These two sources display periodic or quasi-periodic variations in luminosity on the order of tens of days which are known to be superorbital, and are attributed to warped, precessing accretion disks. Using joint NuSTAR and XMM-Newton observations that span a complete superorbital cycle, we examine the broad-band spectra of these sources and find the shape to be well described by an absorbed power law with a soft blackbody component. Changes in spectral shape and pulse profile shape are periodic with superorbital period, as expected from a precessing disk. We perform X-ray tomography using the changes in pulse profiles to model the geometry and kinematics of the inner accretion disk. Our simple beam and inner disk geometric model indicates that the long term changes in soft pulse shape and phase are consistent with reprocessed emission from a precessing inner disk.